Calculus I · Limits and Continuity · exam

Limits and Continuity Practice Exam A

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Practice Examination A

Suggested time: 75 minutes. Calculator: none unless your course normally permits one. Show reasoning; unsupported answers may receive little credit.

Part I: Concepts, 20 points

Exercise 1

A graph approaches 44 from both sides at x=2x=2, but the filled point is (2,7)(2,7). State f(2)f(2) and the limit. Explain the distinction.

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f(2)=7f(2)=7, while the limit is 44. The filled point gives the first; nearby graph behavior gives the second.

Answer 1 from the source-traced unit appendix.
Exercise 2

State all three continuity conditions at x=ax=a.

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Defined value, existing two-sided limit, equality between them.

Answer 2 from the source-traced unit appendix.
Exercise 3

Explain why 0/00/0 is indeterminate rather than equal to zero.

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It records simultaneous numerator and denominator convergence to zero but does not determine their relative rates.

Answer 3 from the source-traced unit appendix.
Exercise 4

State what the Intermediate Value Theorem guarantees and what it does not guarantee.

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IVT guarantees at least one attained intermediate value under continuity; it does not calculate or prove uniqueness.

Answer 4 from the source-traced unit appendix.

Part II: Finite limits, 35 points

Exercise 5

limx2(2x3x+1)\displaystyle\lim_{x\to-2}(2x^3-x+1)

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13-13.

Answer 5 from the source-traced unit appendix.
Exercise 6

limx3x29x3\displaystyle\lim_{x\to3}\frac{x^2-9}{x-3}

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Factor and cancel to obtain x+3x+3; answer 66.

Answer 6 from the source-traced unit appendix.
Exercise 7

limx0x+93x\displaystyle\lim_{x\to0}\frac{\sqrt{x+9}-3}{x}

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Rationalization gives 1/(x+9+3)1/(\sqrt{x+9}+3); answer 1/61/6.

Answer 7 from the source-traced unit appendix.
Exercise 8

limx21x12x2\displaystyle\lim_{x\to2}\frac{\frac1x-\frac12}{x-2}

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Combine fractions to obtain 1/(2x)-1/(2x); at 22, answer 1/4-1/4.

Answer 8 from the source-traced unit appendix.
Exercise 9

limx0sin(7x)2x\displaystyle\lim_{x\to0}\frac{\sin(7x)}{2x}

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(7/2)(sin7x/7x)7/2(7/2)(\sin7x/7x)\to7/2.

Answer 9 from the source-traced unit appendix.
Exercise 10

limx0x2cos(1/x)\displaystyle\lim_{x\to0}x^2\cos(1/x)

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Squeezed between x2-x^2 and x2x^2; answer 00.

Answer 10 from the source-traced unit appendix.
Exercise 11

limx1x1x1\displaystyle\lim_{x\to1}\frac{|x-1|}{x-1}

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Left 1-1, right 11; answer DNE\mathrm{DNE}.

Answer 11 from the source-traced unit appendix.

Part III: Infinite behavior, 25 points

Exercise 12

Find both one-sided limits of x+1x2\dfrac{x+1}{x-2} at x=2x=2.

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Numerator approaches 3>03>0; denominator changes sign. Left -\infty, right ++\infty.

Answer 12 from the source-traced unit appendix.
Exercise 13

limx5x2+12x23x\displaystyle\lim_{x\to-\infty}\frac{5x^2+1}{2x^2-3x}

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5/25/2.

Answer 13 from the source-traced unit appendix.
Exercise 14

limxx2+4x\displaystyle\lim_{x\to-\infty}\frac{\sqrt{x^2+4}}x

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1-1.

Answer 14 from the source-traced unit appendix.
Exercise 15

Find the hole, vertical asymptote, and horizontal asymptote of x21x23x+2\dfrac{x^2-1}{x^2-3x+2}.

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Hole at 11, vertical asymptote x=2x=2, horizontal asymptote y=1y=1.

Answer 15 from the source-traced unit appendix.

Part IV: Continuity and existence, 20 points

Exercise 16

Find kk so {kx+1,x<2,x21,x2\begin{cases}kx+1,&x<2,\\x^2-1,&x\ge2\end{cases} is continuous at 22.

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2k+1=32k+1=3, so k=1k=1.

Answer 16 from the source-traced unit appendix.
Exercise 17

Use IVT to show x3+x3=0x^3+x-3=0 has a root in (1,2)(1,2).

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The polynomial is continuous; values at 1,21,2 are 1,7-1,7, so a root exists.

Answer 17 from the source-traced unit appendix.
Exercise 18

Give a valid δ\delta in terms of ε\varepsilon for limx3(2x+1)=7\lim_{x\to3}(2x+1)=7.

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δ=ε/2\delta=\varepsilon/2.

Answer 18 from the source-traced unit appendix.

After the explanation

Use the section idea

Reading lens

Can you diagnose the limit type and justify a method before beginning the algebra?

Mental model

A mixed problem is a classification task before it is a calculation: direction, substitution result, structure, and required conclusion determine the route.

Decision

Name the limit type and first legal move in a margin note, then solve and check whether the conclusion matches the graph or sign behavior.

Common trap

Pattern matching without diagnosis makes similar-looking problems blur together and hides whether the error was conceptual, algebraic, or strategic.

Check yourself

You are exam-ready when you can choose a method without a section label, explain the choice, and correct a miss by naming its exact cause.

Source & rights

Original instruction with traceable references.

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The verified handoff declares original composition and requires owner provenance review. BetterGrades-original material remains separate from public-domain references; no source textbook PDF is published here.

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

The value a function approaches as its input approaches a target.

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Function
Math glossaryFunction
y=f(x)y=f(x)

A rule or relation assigning exactly one output to each allowed input.

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

At a point, the function value exists and equals the limit there.

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Domain
Math glossaryDomain
domf\operatorname{dom}f

The set of permitted input values.

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Math glossary