AP Calculus AB · Topic 1.5

Determining Limits Using Algebraic Properties Practice

Part of Limits and Continuity.(LIM-1.E)

Practice questions

8

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Sample questions

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  1. Sample 1difficulty 1/5

    Evaluate limx1x2+32x1\displaystyle\lim_{x\to 1}\dfrac{x^2 + 3}{2x - 1}.

    • A

      44

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    • B

      22

    • C

      33

    • D

      55

    Why

    Both top and bottom continuous at x=1x = 1 (denominator 0\ne 0): (1+3)/(21)=4/1=4(1 + 3)/(2 - 1) = 4/1 = 4.

  2. Sample 2difficulty 1/5

    Evaluate limx3(2x25x+1)\displaystyle\lim_{x \to 3}\left(2x^2 - 5x + 1\right).

    • A

      2222

    • B

      00

    • C

      44

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    • D

      1010

    Why

    The polynomial is continuous everywhere, so direct substitution works: 2(9)5(3)+1=1815+1=42(9) - 5(3) + 1 = 18 - 15 + 1 = 4.

  3. Sample 3difficulty 1/5

    Evaluate limxπ/2sinx\displaystyle\lim_{x\to\pi/2} \sin x.

    • A

      22\tfrac{\sqrt 2}{2}

    • B

      11

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    • C

      12\tfrac{1}{2}

    • D

      00

    Why

    sin\sin is continuous everywhere; sin(π/2)=1\sin(\pi/2) = 1.

  4. Sample 4difficulty 1/5

    Evaluate limx1(x3+2x24)\displaystyle\lim_{x\to -1}(x^3 + 2x^2 - 4).

    • A

      7-7

    • B

      1-1

    • C

      3-3

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    • D

      00

    Why

    Polynomial is continuous; substitute: (1)3+2(1)4=1+24=3(-1)^3 + 2(1) - 4 = -1 + 2 - 4 = -3.

  5. Sample 5difficulty 1/5

    Evaluate limx7(π)\displaystyle\lim_{x\to 7}(\pi).

    • A

      Does not exist

    • B

      π\pi

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    • C

      77

    • D

      00

    Why

    Limit of a constant is the constant itself, regardless of xax \to a.