AP Calculus AB · Topic 1.3

Estimating Limit Values from Graphs Practice

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

Practice questions

4

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Sample questions

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  1. Sample 1difficulty 2/5

    x = 1

    The graph has a vertical asymptote at x=1x = 1 with the function going to ++\infty on the right and -\infty... wait, see the graph: left side goes to -\infty, right side from ++\infty. What is limx1f(x)\lim_{x\to 1} f(x)?

    • A

      ++\infty

    • B

      Does not exist

      check_circle
    • C

      -\infty

    • D

      00

    Why

    Left and right one-sided limits diverge to opposite infinities, so the two-sided limit does not exist (and is not ±\pm\infty).

  2. Sample 2difficulty 2/5

    y=3

    From the graph, the open circle at (1,3)(1, 3) shows that limx1f(x)=\displaystyle\lim_{x\to 1} f(x) =

    • A

      11

    • B

      00

    • C

      33

      check_circle
    • D

      Does not exist

    Why

    Both one-sided limits approach 33 even though f(1)f(1) is not defined there.

  3. Sample 3difficulty 2/5

    open f(2) x = 2

    From the graph, limx2f(x)\displaystyle\lim_{x\to 2} f(x) exists because the left and right limits agree (open circle), even though f(2)f(2) (filled circle) is different. The function is

    • A

      Discontinuous at x=2x = 2 — infinite

    • B

      Discontinuous at x=2x = 2 — removable

      check_circle
    • C

      Discontinuous at x=2x = 2 — jump

    • D

      Continuous at x=2x = 2

    Why

    The limit exists but does not equal f(2)f(2). Redefining f(2)f(2) to the common value of the limits would make ff continuous — that's a <strong>removable</strong> discontinuity.

  4. Sample 4difficulty 2/5

    The graph shows ff with limx2f(x)=3\lim_{x\to 2^-}f(x) = 3, limx2+f(x)=5\lim_{x\to 2^+}f(x) = 5, and f(2)=5f(2) = 5. The discontinuity at x=2x = 2 is

    • A

      Removable

    • B

      None

    • C

      Jump

      check_circle
    • D

      Infinite

    Why

    Left and right limits are different finite values → jump discontinuity.