Vocab
Linear function
Math glossaryLinear function
f(x)=mx+bf(x)=mx+b

A function with constant rate of change.

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

The vertical change divided by horizontal change on a nonvertical line.

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

How much one quantity changes per unit change in another.

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

Displays a line's slope and vertical intercept directly.

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

A point where a graph meets the x-axis.

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Math glossary

Graphing a linear equation from standard form

Use intercepts when they are clean, or solve for y when slope and vertical change are more informative.

LaTeX article Updated July 13, 2026

Ax+By=CAx+By=C

Intercepts come from setting one coordinate to zero

At the x-intercept, y is zero. At the y-intercept, x is zero. Substituting those values often creates two points with almost no algebra.

This route is especially efficient when both intercepts are integers. It is less useful when one coefficient is zero or the intercepts are awkward fractions.

2x+3y=12:(6,0), (0,4)2x+3y=12:\quad(6,0),\ (0,4)

Slope-intercept form reveals direction

Solving for y turns standard form into y = mx + b, where m controls the step pattern and b gives a starting point.

Use legal equation moves on every term. Dividing by B means dividing the x-term, the constant, and their signs by B.

Ax+By=Cy=ABx+CBAx+By=C\quad\Rightarrow\quad y=-\frac ABx+\frac CB

A graph needs a check, not just two dots

Substitute a plotted point into the original equation. A point that misses the equation exposes an arithmetic or plotting error immediately.

Vertical lines have the form x = constant and cannot be written as y = mx + b. Horizontal lines have slope zero and the form y = constant.

x=3 is verticaly=2 is horizontalx=3\text{ is vertical}\qquad y=-2\text{ is horizontal}

Worked example

Common mistakes

  • Setting x and y to zero at the same time.
  • Dividing only part of the equation when solving for y.
  • Trying to assign a finite slope to a vertical line.

Keep these ideas

  • Intercepts are coordinate-zero points.
  • Standard and slope-intercept forms describe the same line.
  • Check a plotted point in the original equation.