Mathematics glossary

Read the symbol.
Understand the idea.

213 terms and notations, organized for quick lookup now and a much larger library later.

Our notation conventionsStable anchors · Visual notation · Sitewide definitions
Category
213 entriesAlphabetized A–Z
A13

Absolute-value bars

Also: modulus bars · magnitude

x|x|
Absolute-value bars

Absolute-value bars can also denote magnitude. Their meaning is different from parentheses and from a determinant in later courses.

Absolute-value function

Also: modulus function

f(x)=xf(x)=|x|
Absolute-value function

It equals x for nonnegative inputs and -x for negative inputs.

Alternating series

Also: alternating series test

n=1(1)n1bn\sum_{n=1}^\infty(-1)^{n-1}b_n
Alternating series

The alternating-series test requires decreasing nonnegative magnitudes tending to zero.

Angle symbol

Also: angle notation

ABC\angle ABC
Angle symbol

The middle letter names the vertex when three points identify an angle.

Approximately equal

Also: approximation sign · about equal

π3.14159\pi\approx3.14159
Approximately equal

Use approximate equality after rounding, measurement, or numerical estimation; keep the equals sign for exact identities.

Arc length

Also: curve length

L=ab1+[f(x)]2dxL=\int_a^b\sqrt{1+[f'(x)]^2}\,dx
Arc length

The square-root factor accounts for simultaneous horizontal and vertical change.

Area between curves

Also: area between graphs

A=ab(f(x)g(x))dxA=\int_a^b(f(x)-g(x))\,dx
Area between curves

Find intersections and confirm which curve is above on each interval before integrating.

Area under a curve

Also: area beneath graph

A=abf(x)dxA=\int_a^b|f(x)|\,dx
Area under a curve

A plain definite integral gives signed area; absolute value or interval splitting is needed for total geometric area across sign changes.

Associative property

Also: associativity

(a+b)+c=a+(b+c)(a+b)+c=a+(b+c)
Associative property

Subtraction and division are not associative unless rewritten using inverses.

Asymptote

Also: vertical asymptote · horizontal asymptote

x=aory=bx=a\quad\text{or}\quad y=b
Asymptote

Graphs may approach an asymptote without crossing restrictions implied by the function's domain.

Average value of a function

Also: mean value of function

favg=1baabf(x)dxf_{\rm avg}=\frac1{b-a}\int_a^b f(x)\,dx
Average value of a function

It is the constant height producing the same signed area over the interval.

B2

Binomial

Also: two-term polynomial

x+5x+5
Binomial

Many factoring patterns, including difference of squares, apply to special binomials.

Braces

Also: curly braces

{x:x>0}\{x:x>0\}
Braces

Visible braces usually enclose a set. In LaTeX source, braces also group material without necessarily printing.

C14

Chain rule

Also: chain differentiation

ddxf(g(x))=f(g(x))g(x)\frac d{dx}f(g(x))=f'(g(x))g'(x)
Chain rule

Differentiate the outer function at the unchanged inner expression, then multiply by the inner derivative.

Full explanation, notation, and worked example →

Closed interval

Also: included endpoints

[a,b][a,b]
Closed interval

A closed finite interval contains its endpoints and every real number between them.

Coefficient

Also: multiplier

7x7x
Coefficient

In 7x, the coefficient of x is 7. A missing visible coefficient is often 1 or -1.

Commutative property

Also: commutativity

a+b=b+aa+b=b+a
Commutative property

Subtraction, division, and function composition are generally not commutative.

Comparison test

Also: direct comparison

0anbn0\le a_n\le b_n
Comparison test

An upper bound by a convergent positive series proves convergence; a lower bound by a divergent one proves divergence.

Completing the square

Also: complete the square

x2+bx=(x+b2)2(b2)2x^2+bx=\left(x+\frac b2\right)^2-\left(\frac b2\right)^2
Completing the square

The method reveals vertex form and provides a general route to the quadratic formula.

Concavity

Also: concave up · concave down

f(x)>0concave upf''(x)>0\Rightarrow\text{concave up}
Concavity

The second derivative gives a common concavity test where it exists.

Conditional convergence

Also: conditionally convergent

an converges,an diverges\sum a_n\ \text{converges},\quad\sum|a_n|\ \text{diverges}
Conditional convergence

Conditionally convergent series are sensitive to rearrangement in ways absolutely convergent series are not.

Constant

Also: fixed value

c=5c=5
Constant

A constant does not change within the stated context, even though another problem may assign it a different value.

Constant of integration

Also: plus C · integration constant

+C+C
Constant of integration

Better Grades reserves uppercase C for this convention and omits it from definite-integral values.

Continuity

Also: continuous function

limxaf(x)=f(a)\lim_{x\to a}f(x)=f(a)
Continuity

Continuity joins existence of f(a), existence of the nearby limit, and equality between them.

Full explanation, notation, and worked example →

Convergence

Also: convergent

anLa_n\to L
Convergence

For a series, convergence means its partial sums approach a finite number.

Coordinate plane

Also: Cartesian plane

(x,y)(x,y)
Coordinate plane

The x-axis is horizontal, the y-axis is vertical, and their intersection is the origin.

Critical number

Also: critical point

f(c)=0 or undefinedf'(c)=0\ \text{or undefined}
Critical number

Critical numbers are candidates for extrema, not automatic maxima or minima.

Full explanation, notation, and worked example →
D22

Definite integral

Also: bounded integral

abf(x)dx\int_a^b f(x)\,dx
Definite integral

A definite integral is a number when the bounds and function are fixed; it is not an antiderivative family.

Full explanation, notation, and worked example →

Degree

Also: degree of polynomial

deg(4x3x)=3\deg(4x^3-x)=3
Degree

Degree describes leading growth and helps predict the maximum number of roots.

Degree symbol

Also: degrees

9090^\circ
Degree symbol

A full turn is 360 degrees. Calculus formulas normally use radians unless degrees are explicitly stated.

Delta

Also: change symbol

Δy=y2y1\Delta y=y_2-y_1
Delta

Uppercase delta commonly means a change between two values. Lowercase delta often names a small positive tolerance.

Denominator

Also: bottom of fraction

ab\frac{a}{\color{#df5f3f}{b}}
Denominator

The denominator names the divisor and imposes a nonzero restriction.

Dependent variable

Also: output variable

y=f(x)y=f(x)
Dependent variable

In y=f(x), y is dependent because the rule determines it from x.

Derivative

Also: differentiate · differentiation · instantaneous rate

ddx[f(x)]\frac d{dx}[f(x)]
operator notation
dydx\frac{dy}{dx}
dependent-variable notation
f(x)f'(x)
prime notation
y˙\dot y
time-derivative notation

A derivative is the limit of average rates over shrinking intervals. It is also the slope of the tangent line when that geometric interpretation applies.

Full explanation, notation, and worked example →

Derivative at a point

Also: instantaneous slope

f(a)f'(a)
Derivative at a point

This number is the instantaneous rate and tangent slope at x=a, when the derivative exists.

Derivative notations

Also: d/dx · dy/dx · f prime · dot f

ddx[f(x)]\frac d{dx}[f(x)]
derivative operator
dydx=f(x)\frac{dy}{dx}=f'(x)
dependent-variable and prime notation
f˙=dfdt\dot f=\frac{df}{dt}
time derivative

d/dx is an operator; dy/dx is the derivative of y with respect to x; f'(x) names the derivative of f; and a dot conventionally means a time derivative.

Derivative operator

Also: d over dx · d/dx

ddx\frac{d}{dx}
Derivative operator

The operator d/dx acts on the expression that follows. By itself it is an instruction, not yet a derivative value.

Difference of squares

Also: square difference

a2b2=(ab)(a+b)a^2-b^2=(a-b)(a+b)
Difference of squares

Both terms must be squares and the operation must be subtraction over the real numbers.

Difference quotient

Also: derivative quotient

f(x+h)f(x)h\frac{f(x+h)-f(x)}h
Difference quotient

The quotient is formed for nonzero h; the derivative comes from its limit as h approaches zero.

Differential

Also: dx · dy

dxdx
Differential

In an integral, dx states the variable of accumulation. In differential notation, dy=f'(x)dx records a linear change relationship.

Differentiation

Also: taking a derivative

fff\mapsto f'
Differentiation

Differentiation applies limit definitions or valid derivative rules while preserving the named independent variable.

Direct variation

Also: direct proportion

y=kxy=kx
Direct variation

The constant k is both y/x and the line's slope.

Discontinuity

Also: break in graph

limxaf(x)f(a)\lim_{x\to a}f(x)\ne f(a)
Discontinuity

A discontinuity may be removable, a jump, infinite, or oscillatory depending on the failure.

Discriminant

Also: b squared minus 4ac

Δ=b24ac\Delta=b^2-4ac
Discriminant

A positive discriminant gives two real roots, zero gives one repeated real root, and a negative value gives nonreal conjugates.

Distributive property

Also: distribute

a(b+c)=ab+aca(b+c)=ab+ac
Distributive property

Distribution preserves equivalence and works in reverse when factoring.

Divergence

Also: divergent

an↛La_n\not\to L
Divergence

Divergence can mean unbounded growth, oscillation, or another failure of a required limit.

Division symbol

Also: obelus

a÷ba\div b
Division symbol

Better Grades usually uses a fraction bar in algebra because it makes grouping explicit.

Domain

Also: input set

domf\operatorname{dom}f
Domain

A formula's domain excludes inputs that make an operation undefined, and a model may impose additional contextual restrictions.

Dot notation

Also: Newton notation · y dot

y˙, y¨\dot y,\ \ddot y
Dot notation

A dot over a quantity conventionally means one time derivative; two dots mean the second time derivative.

E13

Element

Also: member

2A2\in A
Element

Membership uses the element-of symbol; it is different from being a subset.

Elimination method

Also: linear combination

ax+by=cax+dy=e\begin{aligned}ax+by&=c\\-ax+dy&=e\end{aligned}
Elimination method

Scaling and adding or subtracting aligned equations can reduce a system to one variable.

Ellipsis

Also: dots

1,2,3,1,2,3,\ldots
Ellipsis

Dots omit intermediate terms only when the continuation rule is clear from context.

Empty set

Also: null set

\varnothing
Empty set

The empty set is a set, not the number zero and not a missing answer.

Equals sign

Also: equality sign

a=ba=b
Equals sign

The equals sign joins expressions that are equal. It should not be used merely to mean “the next line.”

Equation

Also: equality

2x+3=112x+3=11
Equation

Solving an equation means finding the permitted values that make its equality true.

Equivalent expressions

Also: equivalent forms

2(x+3)=2x+62(x+3)=2x+6
Equivalent expressions

Equivalence may depend on domain restrictions; canceling a factor does not restore an excluded input.

Euler's number

Also: natural base · Euler number

e2.71828e\approx2.71828
Euler's number

Euler's number is the base whose exponential function is its own derivative.

Evaluation bar

Also: bounds bar

F(x)abF(x)\big|_a^b
Evaluation bar

The evaluation bar means F(b) minus F(a). It is not an absolute-value bar in this context.

Exponent notation

Also: power notation · superscript

ana^n
Exponent notation

The superscript is the exponent. Its meaning extends from positive integers to zero, negative, rational, and real exponents under appropriate domain rules.

Exponential function

Also: exponential model

f(x)=abxf(x)=ab^x
Exponential function

With positive base b not equal to one, the function models repeated multiplicative change.

Expression

Also: algebraic expression

2x+32x+3
Expression

An expression can be evaluated or simplified, but it is not solved until it appears in a statement such as an equation.

Extraneous solution

Also: extraneous root

candidate⇏solution\text{candidate}\not\Rightarrow\text{solution}
Extraneous solution

Squaring, clearing denominators, and some other nonreversible steps can introduce extraneous candidates.

F8

Factor

Also: multiplicative factor

(x2)(x+3)(x-2)(x+3)
Factor

Factors may cancel only across a product and only when their nonzero restrictions are retained.

Factorial

Also: factorial sign

n!=n(n1)1n!=n(n-1)\cdots1
Factorial

For a nonnegative integer n, n factorial is the product from n down to 1, with 0! defined as 1.

Factoring

Also: factorization

x29=(x3)(x+3)x^2-9=(x-3)(x+3)
Factoring

Factoring exposes zeros, common structure, and legal cancellations.

Fraction bar

Also: vinculum · division bar

ab\frac{a}{b}
Fraction bar

A fraction bar groups the entire numerator and denominator and means division, provided the denominator is nonzero.

Function

Also: mapping

y=f(x)y=f(x)
Function

Different inputs may share an output, but one allowed input cannot have two outputs in a function.

Function composition

Also: circle operator · composite function

(fg)(x)=f(g(x))(f\circ g)(x)=f(g(x))
Function composition

Composition is evaluated from the inside outward and is generally not commutative.

Function notation

Also: f of x

f(x)f(x)
Function notation

The parentheses identify the input to f; f(x) does not mean f multiplied by x.

Fundamental theorem of calculus

Also: FTC

abf(x)dx=F(b)F(a)\int_a^b f(x)\,dx=F(b)-F(a)
Fundamental theorem of calculus

When F'=f under the theorem's hypotheses, endpoint evaluation computes the definite integral.

Full explanation, notation, and worked example →
G5

Greater than or equal

Also: at least · geq

xax\ge a
Greater than or equal

The symbol combines an order comparison with equality, so the endpoint is included.

Greater-than sign

Also: greater than

a>ba>b
Greater-than sign

The open side faces the larger value and the point faces the smaller value.

Greatest common factor

Also: GCF · greatest common divisor

GCF(12x2,18x)=6x\operatorname{GCF}(12x^2,18x)=6x
Greatest common factor

Factoring out the GCF is the first check before applying more specialized patterns.

Growth factor

Also: decay factor

b=1+rb=1+r
Growth factor

Growth uses b greater than one; decay uses a factor between zero and one.

I25

Identity

Also: algebraic identity

(a+b)2=a2+2ab+b2(a+b)^2=a^2+2ab+b^2
Identity

An identity differs from a conditional equation, which is true only for particular solutions.

If and only if

Also: iff · biconditional

PQP\Longleftrightarrow Q
If and only if

A biconditional records two implications and therefore an equivalence of conditions.

Imaginary unit

Also: i

i2=1i^2=-1
Imaginary unit

The imaginary unit extends the real numbers to the complex numbers. It is not an index when used in this role.

Implicit differentiation

Also: implicit derivative

ddxf(x,y)=fx+fydydx\frac d{dx}f(x,y)=f_x+f_y\frac{dy}{dx}
Implicit differentiation

Every y-dependent term receives a dy/dx factor because y is treated as a function of x.

Full explanation, notation, and worked example →

Implies

Also: right arrow · therefore implies

PQP\Rightarrow Q
Implies

An implication runs in one direction. Its reverse requires separate justification.

Indefinite integral

Also: antiderivative integral

f(x)dx=F(x)+C\int f(x)\,dx=F(x)+C
Indefinite integral

The constant C is required because differentiation removes additive constants.

Independent variable

Also: input variable

y=f(x)y=f(x)
Independent variable

In y=f(x), x is the independent variable unless the context defines another dependency.

Indeterminate form

Also: 0 over 0 · infinity over infinity

00,\frac00,\quad\frac\infty\infty
Indeterminate form

Different functions can share an indeterminate form and have different limits, so further analysis is required.

Index

Also: subscript index

ana_n
Index

Indices are conventionally lowercase integers such as n, k, i, or j, with their starting value stated.

Inequality

Also: order statement

x<4x<4
Inequality

An inequality often has an interval or union of intervals as its solution set.

Infinite limit

Also: unbounded limit

limxaf(x)=\lim_{x\to a}f(x)=\infty
Infinite limit

The infinity symbol records unbounded behavior rather than a real-valued limit.

Infinity symbol

Also: infinity

xx\to\infty
Infinity symbol

Infinity indicates that a quantity grows without bound. Ordinary arithmetic rules for finite numbers do not automatically apply to it.

Inflection point

Also: point of inflection

f changes signf''\text{ changes sign}
Inflection point

A zero or undefined second derivative is only a candidate; the concavity must actually switch.

Input

Also: independent value

f(3)f(3)
Input

The input belongs to the domain and is commonly written inside function parentheses.

Integers

Also: Z · integer set

Z\mathbb{Z}
Integers

The integers contain no fractional part and extend without bound in both directions.

Integral symbol

Also: integration sign

f(x)dx\int f(x)\,dx
Integral symbol

The elongated S recalls summation. Bounds make the integral definite; no bounds usually asks for a family of antiderivatives.

Integral test

Also: integral convergence test

anf(x)dx\sum a_n\quad\leftrightarrow\quad\int f(x)\,dx
Integral test

Under the test's continuity, positivity, and decrease conditions, the series and integral converge or diverge together.

Integrand

Also: inside integral

f(x)integranddx\int \underbrace{f(x)}_{\text{integrand}}\,dx
Integrand

The integrand includes its algebraic structure but not the integral sign, bounds, or differential.

Integration by parts

Also: parts formula · IBP

udv=uvvdu\int u\,dv=uv-\int v\,du
Integration by parts

Choose u so differentiation simplifies it and dv so it can be integrated cleanly.

Full explanation, notation, and worked example →

Intersection

Also: cap symbol

ABA\cap B
Intersection

Intersection corresponds to “and” between membership conditions.

Interval

Also: interval notation

a<xba<x\le b
Interval

Parentheses exclude endpoints and brackets include them. Infinity always uses a parenthesis.

Inverse function

Also: functional inverse

f1(f(x))=xf^{-1}(f(x))=x
Inverse function

An inverse function is not the reciprocal 1/f(x). Its domain and range exchange roles with the original.

Inverse operation

Also: undo operation

x+33=xx+3-3=x
Inverse operation

Equation solving uses inverse operations while applying the same legal move to both sides.

Inverse variation

Also: inverse proportion

y=kxy=\frac{k}{x}
Inverse variation

As one nonzero quantity grows, the other shrinks so xy=k.

L13

Leading coefficient

Also: leading number

5x4+5x^4+\cdots
Leading coefficient

The leading coefficient and degree control a polynomial's end behavior.

Less than or equal

Also: at most · leq

xbx\le b
Less than or equal

The symbol combines an order comparison with equality, so the endpoint is included.

Less-than sign

Also: less than

a<ba<b
Less-than sign

The point faces the smaller value and the open side faces the larger value.

Like terms

Also: similar terms

3x2+5x2=8x23x^2+5x^2=8x^2
Like terms

Only coefficients of like terms combine; unlike powers remain separate.

Limit

Also: limiting value

limxaf(x)=L\lim_{x\to a}f(x)=L
Limit

A limit describes nearby behavior and may exist even when the function is undefined or has another value at the target.

Full explanation, notation, and worked example →

Limit comparison test

Also: limit comparison

limnanbn=c\lim_{n\to\infty}\frac{a_n}{b_n}=c
Limit comparison test

A finite positive c means the two positive-term series share convergence behavior.

Line

Also: straight line · ell

:y=mx+b\ell:y=mx+b
Line

A lowercase script ell may name a geometric line; this prevents confusion with an ordinary scalar variable.

Linear equation

Also: first-degree equation

ax+b=cax+b=c
Linear equation

A one-variable linear equation has one, no, or infinitely many solutions after simplification.

Linear function

Also: line function

f(x)=mx+bf(x)=mx+b
Linear function

Its graph is a nonvertical line, with slope m and vertical intercept b.

Linearization

Also: linear approximation

L(x)=f(a)+f(a)(xa)L(x)=f(a)+f'(a)(x-a)
Linearization

Linearization is most accurate near a and needs an error discussion when used farther away.

Logarithm

Also: log

logbx=yby=x\log_b x=y\Longleftrightarrow b^y=x
Logarithm

A logarithm is defined for positive arguments and is the inverse of an exponential function with the same base.

M7

Maclaurin series

Also: Maclaurin expansion

n=0f(n)(0)n!xn\sum_{n=0}^\infty\frac{f^{(n)}(0)}{n!}x^n
Maclaurin series

Maclaurin notation simplifies common expansions around the origin.

Maps-to arrow

Also: mapsto

xx2x\mapsto x^2
Maps-to arrow

The maps-to arrow separates an input pattern from the output assigned by a rule.

Mathematical model

Also: model

y=f(t)y=f(t)
Mathematical model

A model includes assumptions, units, and a useful domain; matching data alone does not make it universally valid.

Mean value theorem

Also: MVT

f(c)=f(b)f(a)baf'(c)=\frac{f(b)-f(a)}{b-a}
Mean value theorem

If f is continuous on [a,b] and differentiable on (a,b), at least one c in the open interval satisfies the equation.

Monomial

Also: one-term polynomial

7x37x^3
Monomial

A monomial coefficient may be any real number and its variable exponents are nonnegative integers.

Multiplication cross

Also: times sign

a×ba\times b
Multiplication cross

The cross means multiplication in elementary contexts, but later it can denote a vector cross product or Cartesian product.

Multiplication dot

Also: center dot

aba\cdot b
Multiplication dot

The centered dot is useful between numbers, units, or complicated factors where adjacency could be ambiguous.

N9

Nabla

Also: del operator · gradient symbol

f\nabla f
Nabla

Nabla is read “del.” In multivariable calculus it combines partial-derivative directions.

Natural logarithm

Also: ln

lnx\ln x
Natural logarithm

The natural logarithm is defined for positive real x and appears naturally in calculus and continuous growth.

Natural numbers

Also: N · counting numbers

N\mathbb{N}
Natural numbers

Conventions differ about whether zero is natural, so Better Grades states the starting index when it matters.

Negation slash

Also: not symbol · slashed relation

P⇏QP\not\Rightarrow Q
Negation slash

The not command places a slash through a relation. Read the resulting combined symbol as one negated statement, not as subtraction.

Negative exponent

Also: negative power

an=1ana^{-n}=\frac1{a^n}
Negative exponent

A negative exponent does not make the base negative; it records reciprocal multiplication.

Newton's method

Also: Newton-Raphson method

xn+1=xnf(xn)f(xn)x_{n+1}=x_n-\frac{f(x_n)}{f'(x_n)}
Newton's method

Success depends on a sensible starting value and nonzero derivatives; convergence is not automatic.

Not in

Also: not an element of

xAx\notin A
Not in

The slashed membership symbol excludes the left-hand object from the set on the right.

Not-equal sign

Also: not equal · neq

aba\ne b
Not-equal sign

The not-equal sign excludes equality between the quantities on its two sides.

Numerator

Also: top of fraction

ab\frac{\color{#df5f3f}{a}}{b}
Numerator

The numerator is the quantity being divided. It may contain several grouped terms.

O5

One-sided limit

Also: left-hand limit · right-hand limit

limxaf(x),limxa+f(x)\lim_{x\to a^-}f(x),\quad\lim_{x\to a^+}f(x)
One-sided limit

One-sided limits describe a single branch near a boundary or jump.

Full explanation, notation, and worked example →

Open interval

Also: excluded endpoints

(a,b)(a,b)
Open interval

Every point between a and b is included, while a and b are not.

Optimization

Also: optimization problem · maximize · minimize

f(c)=0,acbf'(c)=0,\quad a\le c\le b
Optimization

A calculus optimization argument builds a one-variable objective, states its feasible domain, finds candidates, and verifies the requested extremum.

Full explanation, notation, and worked example →

Ordered pair

Also: coordinate pair

(x,y)(x,y)
Ordered pair

In the coordinate plane, the first coordinate is horizontal and the second is vertical.

Output

Also: dependent value

f(3)=7f(3)=7
Output

Outputs form the range and may be described by a dependent variable such as y.

P21

p-series

Also: p series test

n=11np\sum_{n=1}^\infty\frac1{n^p}
p-series

The p-series converges exactly when p is greater than one.

Parabola

Also: quadratic graph

y=a(xh)2+ky=a(x-h)^2+k
Parabola

Its opening direction and width depend on a, while its vertex and axis come from h and k.

Parallel

Also: parallel lines

12\ell_1\parallel\ell_2
Parallel

Distinct nonvertical parallel lines have equal slopes and different intercepts.

Parameter

Also: model parameter

y=mx+by=mx+b
Parameter

Parameters such as m and b choose one member of a model family; variables then range within that chosen model.

Parentheses

Also: round brackets

f(x+1)f(x+1)
Parentheses

Parentheses control operation order and enclose function arguments. They also mark excluded interval endpoints.

Partial fractions

Also: partial fraction decomposition

p(x)q(x)=axr\frac{p(x)}{q(x)}=\sum\frac{a}{x-r}
Partial fractions

Factor the denominator, choose a template, solve coefficients, then integrate or simplify the pieces.

Partial sum

Also: nth partial sum

Sn=k=1nakS_n=\sum_{k=1}^n a_k
Partial sum

A series converges when the sequence of partial sums S_n converges.

Partial-derivative symbol

Also: partial d

fx\frac{\partial f}{\partial x}
Partial-derivative symbol

The rounded partial symbol distinguishes a partial derivative from an ordinary single-variable derivative.

Percent

Also: percentage

p%=p100p\%=\frac p{100}
Percent

Convert a percent to a decimal by dividing by 100 before using it as a multiplier.

Perfect-square trinomial

Also: square trinomial

a2+2ab+b2=(a+b)2a^2+2ab+b^2=(a+b)^2
Perfect-square trinomial

The first and last terms are squares and the middle term is twice their signed product.

Perpendicular

Also: right angle

12\ell_1\perp\ell_2
Perpendicular

For nonvertical lines in the coordinate plane, perpendicular slopes are negative reciprocals.

Pi

Also: circle constant

π3.14159\pi\approx3.14159
Pi

Pi is an exact irrational constant used throughout geometry, trigonometry, and calculus.

Piecewise function

Also: piecewise definition

f(x)={x,x<0x2,x0f(x)=\begin{cases}x,&x<0\\x^2,&x\ge0\end{cases}
Piecewise function

Each input must be evaluated with the rule whose condition contains it.

Plus-or-minus sign

Also: plus minus · pm

x=±kx=\pm\sqrt{k}
Plus-or-minus sign

The plus-or-minus sign abbreviates two statements: one using plus and one using minus.

Point-slope form

Also: point slope

yy1=m(xx1)y-y_1=m(x-x_1)
Point-slope form

The form is especially useful when the y-intercept is not known.

Polynomial

Also: polynomial expression

anxn++a1x+a0a_nx^n+\cdots+a_1x+a_0
Polynomial

Polynomial degree is the largest exponent with a nonzero coefficient.

Power series

Also: series in powers

n=0cn(xa)n\sum_{n=0}^\infty c_n(x-a)^n
Power series

A power series converges inside a radius, diverges outside it, and needs endpoint checks.

Full explanation, notation, and worked example →

Prime notation

Also: f prime · apostrophe notation

f(x), f(x)f'(x),\ f''(x)
Prime notation

One prime means the first derivative; additional primes indicate higher derivatives. The independent variable is inferred from the function input.

Product rule

Also: derivative of product

(fg)=fg+fg(fg)'=f'g+fg'
Product rule

Differentiating each factor and multiplying the results is not the product rule.

Product symbol

Also: product notation · capital pi

k=1nak\prod_{k=1}^{n}a_k
Product symbol

Capital pi notation is the multiplicative counterpart of summation notation.

Proportion

Also: equal ratios

ab=cd\frac ab=\frac cd
Proportion

A proportion can be solved by valid equation operations; cross multiplication is shorthand when denominators are nonzero.

Q3

Quadratic

Also: second-degree

ax2+bx+cax^2+bx+c
Quadratic

A quadratic graph is a parabola and may have zero, one, or two real zeros.

Quadratic formula

Also: quadratic equation formula

x=b±b24ac2ax=\frac{-b\pm\sqrt{b^2-4ac}}{2a}
Quadratic formula

The formula follows from completing the square and works even when a quadratic does not factor nicely.

Quotient rule

Also: derivative of quotient

(fg)=fgfgg2\left(\frac fg\right)'=\frac{f'g-fg'}{g^2}
Quotient rule

The rule applies where g is nonzero and keeps the numerator order significant.

R17

Radical

Also: root expression

an\sqrt[n]{a}
Radical

Simplifying a radical removes perfect-power factors while respecting real-domain restrictions.

Radical symbol

Also: root sign · square root symbol

xn\sqrt[n]{x}
Radical symbol

The small index names the root. An even real root requires a nonnegative radicand.

Range

Also: output set

rangef\operatorname{range}f
Range

Range depends on both the rule and its domain. It is not automatically every real number.

Rate of change

Also: rate

ΔyΔx\frac{\Delta y}{\Delta x}
Rate of change

Average rate uses finite changes; instantaneous rate is described by a derivative.

Ratio

Also: comparison

a:b=aba:b=\frac ab
Ratio

A ratio compares quantities in a stated order and should preserve meaningful units.

Ratio test

Also: d'Alembert ratio test

L=limnan+1anL=\lim_{n\to\infty}\left|\frac{a_{n+1}}{a_n}\right|
Ratio test

The series converges absolutely if L<1, diverges if L>1, and the test is inconclusive if L=1.

Rational equation

Also: fraction equation

p(x)q(x)=r(x)s(x)\frac{p(x)}{q(x)}=\frac{r(x)}{s(x)}
Rational equation

Record denominator restrictions before clearing fractions, then check candidates in the original equation.

Rational exponent

Also: fractional exponent

am/n=amna^{m/n}=\sqrt[n]{a^m}
Rational exponent

Real-domain restrictions depend on the root index and the base.

Rational expression

Also: algebraic fraction

p(x)q(x)\frac{p(x)}{q(x)}
Rational expression

Zeros of the original denominator are excluded even if a common factor later cancels.

Real numbers

Also: R · reals

R\mathbb{R}
Real numbers

The real numbers include rational and irrational numbers but not nonreal complex values.

Reciprocal

Also: multiplicative inverse

a1aa\mapsto\frac1a
Reciprocal

A quantity times its reciprocal equals one. Zero has no reciprocal.

Related rates

Also: rates problem

ddtf(x(t),y(t))=0\frac d{dt}f(x(t),y(t))=0
Related rates

Differentiate the constraint with respect to time before inserting the values at the requested instant.

Full explanation, notation, and worked example →

Relation

Also: input-output relation

{(x,y)}\{(x,y)\}
Relation

A relation becomes a function only when each input is paired with no more than one output.

Removable discontinuity

Also: hole

limxaf(x)=Lf(a)\lim_{x\to a}f(x)=L\ne f(a)
Removable discontinuity

Defining or redefining f(a)=L repairs continuity without changing nearby values.

Rolle's theorem

Also: Rolle theorem

f(a)=f(b)f(c)=0f(a)=f(b)\Rightarrow f'(c)=0
Rolle's theorem

Rolle's theorem is the equal-endpoint special case of the mean value theorem.

Root test

Also: Cauchy root test

L=limnannL=\lim_{n\to\infty}\sqrt[n]{|a_n|}
Root test

The conclusion rule matches the ratio test and is especially useful when the nth term is raised to the nth power.

S18

Secant line

Also: secant slope

msec=f(b)f(a)bam_{\rm sec}=\frac{f(b)-f(a)}{b-a}
Secant line

Its slope is the average rate of change across the interval from a to b.

Set

Also: collection

A={1,2,3}A=\{1,2,3\}
Set

A set is determined by membership, not by the order in which elements are listed.

Set membership

Also: element of · in symbol

xAx\in A
Set membership

The membership symbol relates an element on the left to a set on the right.

Slope

Also: gradient · rise over run

m=ΔyΔxm=\frac{\Delta y}{\Delta x}
Slope

Slope records a constant rate of change for a line. A vertical line has undefined slope.

Slope-intercept form

Also: y equals mx plus b

y=mx+by=mx+b
Slope-intercept form

m is the slope and (0,b) is the y-intercept.

Solution

Also: root · answer

x=4x=4
Solution

A candidate becomes a solution only after it satisfies the original equation, inequality, or system and its domain restrictions.

Solution set

Also: answer set

{x:x2}\{x:x\ge2\}
Solution set

A solution set may be finite, an interval, a union, empty, or an entire allowed domain.

Square brackets

Also: brackets

[a,b][a,b]
Square brackets

In interval notation, square brackets mean the endpoint is included. In formulas they can provide a second grouping level.

Squeeze theorem

Also: sandwich theorem

g(x)f(x)h(x)g(x)\le f(x)\le h(x)
Squeeze theorem

When g and h approach the same value, the trapped function f must approach it too.

Standard form of a line

Also: standard form

Ax+By=CAx+By=C
Standard form of a line

By site convention, uppercase A, B, and C are reserved here for the traditional standard-form coefficients.

Subscript notation

Also: index notation

ana_n
Subscript notation

A subscript distinguishes members of a sequence, coordinates, parameters, or related quantities.

Subset

Also: contained in

ABA\subseteq B
Subset

The subset-or-equal symbol allows the two sets to be identical. A strict subset convention should be stated when ambiguity matters.

Substitution method

Also: solve by substitution

y=f(x)g(x,y)=g(x,f(x))y=f(x)\Rightarrow g(x,y)=g(x,f(x))
Substitution method

Substitution reduces a system when one variable is already isolated or easy to isolate.

Summation symbol

Also: sigma · sum sign

k=1nak\sum_{k=1}^{n}a_k
Summation symbol

Sigma notation states the index, starting value, ending value, and expression to add.

Surface area of revolution

Also: surface of revolution

S=2πabr(x)dsS=2\pi\int_a^b r(x)\,ds
Surface area of revolution

The integrand combines circumference with the curve's arc-length element.

System of equations

Also: simultaneous equations

{f(x,y)=0g(x,y)=0\begin{cases}f(x,y)=0\\g(x,y)=0\end{cases}
System of equations

A system may have one solution, none, or infinitely many depending on how its constraints intersect.

T7

Tangent line

Also: tangent

yf(a)=f(a)(xa)y-f(a)=f'(a)(x-a)
Tangent line

When differentiability holds, its slope is the derivative at the point.

Taylor remainder

Also: error term · Taylor error

Rn(x)=f(x)Tn(x)R_n(x)=f(x)-T_n(x)
Taylor remainder

A remainder bound turns a finite approximation into a quantitative accuracy statement.

Taylor series

Also: Taylor expansion

n=0f(n)(a)n!(xa)n\sum_{n=0}^\infty\frac{f^{(n)}(a)}{n!}(x-a)^n
Taylor series

The series represents f only where its remainder approaches zero.

Full explanation, notation, and worked example →

Term

Also: algebraic term

3x22x+53x^2-2x+5
Term

Signs belong to their terms. Factors inside one term are multiplied together.

Transition arrow

Also: long arrow · becomes arrow

x=3:x2(3)2x=-3:\quad x^2\longrightarrow(-3)^2
Transition arrow

A long transition arrow organizes a calculation or approach. It does not automatically assert the logical implication represented by a double arrow.

Trinomial

Also: three-term polynomial

x2+5x+6x^2+5x+6
Trinomial

Quadratic trinomials often factor into two binomials when suitable numbers exist.

Two-sided limit

Also: ordinary limit

limxaf(x)=L\lim_{x\to a}f(x)=L
Two-sided limit

A finite two-sided limit exists exactly when both one-sided limits exist and equal the same value.

U4

u-substitution

Also: substitution rule · change of variable

u=g(x),du=g(x)dxu=g(x),\quad du=g'(x)\,dx
u-substitution

A useful substitution absorbs an inner expression and its differential factor, with bounds changed for definite integrals.

Full explanation, notation, and worked example →

Union

Also: cup symbol

ABA\cup B
Union

Union corresponds to an inclusive “or” between membership conditions.

Unit rate

Also: per unit

60 mi1 h\frac{60\ \mathrm{mi}}{1\ \mathrm h}
Unit rate

Unit rates make proportional comparisons and dimensional interpretation easier.

Units

Also: measurement units · dimensions

5 m/s5\ \mathrm{m/s}
Units

Units participate in multiplication and division and provide a strong check on formulas and answers.

V3

Variable

Also: unknown

xx
Variable

A variable represents a quantity. Better Grades uses lowercase italic letters for ordinary scalar variables unless a documented convention requires otherwise.

Vertex

Also: turning point

(h,k)(h,k)
Vertex

In vertex form y=a(x-h)^2+k, the vertex is (h,k) and the axis is x=h.

Volume of revolution

Also: washer method · shell method

V=πab(R2r2)dxV=\pi\int_a^b(R^2-r^2)\,dx
Volume of revolution

Washers use outer and inner radii; shells use circumference, radius, and height.

W1

Work

Also: work done

W=abF(x)dxW=\int_a^b F(x)\,dx
Work

When force varies with position, the work integral adds force times small displacement.

X1

x-intercept

Also: horizontal intercept · zero

f(x)=0f(x)=0
x-intercept

At an x-intercept the output coordinate is zero, so finding intercepts often means solving f(x)=0.

Y1

y-intercept

Also: vertical intercept

f(0)f(0)
y-intercept

At a y-intercept the input coordinate is zero, provided zero belongs to the domain.

Z1

Zero-product property

Also: zero factor property

ab=0a=0 or b=0ab=0\Rightarrow a=0\ \text{or}\ b=0
Zero-product property

The property applies after one side of an equation has been set equal to zero and the other side is factored.