Home / AP Calculus AB: 1.2 Defining Limits – Exam Style questions – MCQ

AP Calculus AB: 1.2 Defining Limits – Exam Style questions – MCQ

Question

Graph of function f(x) showing behavior around x=2

The graph of the function f is shown above. What is \(\lim_{x\rightarrow 2}f(x)\)?

A) \(\frac{1}{2}\)
B) 1
C) 4
D) The limit does not exist

▶️ Answer/Explanation

Solution

Correct Answer: C

– The limit as x approaches 2 is determined by the function’s behavior NEAR x=2, not AT x=2
– From the graph, as x approaches 2 from both sides (left and right), f(x) approaches 4
– This occurs despite the actual value at f(2) being 1 (shown by the solid dot)

Key observations:
• Left-hand limit (x→2⁻): Approaches 4
• Right-hand limit (x→2⁺): Approaches 4
• Since both one-sided limits agree, the limit exists and equals 4

Why other options are incorrect:
– A) 1/2: Not supported by the graph’s behavior
– B) 1: This is f(2), not the limit
– D: Incorrect because the limit does exist (both sides agree)

The limit is about the approaching behavior, not the actual value at the point.

Question

Graph of function f(x) showing behavior around x=2

The graph of the function f is shown above. What is \(\lim_{x\rightarrow 2}f(x)\)?

A) 0
B) 1
C) 2
D) The limit does not exist

▶️ Answer/Explanation

Solution

Correct Answer: C

– The limit as x approaches 2 is determined by the function’s behavior NEAR x=2, not AT x=2
– From the graph, as x approaches 2 from both sides (left and right), f(x) approaches 2
– This occurs despite the actual value at f(2) being 1 (shown by the point discontinuity)

Key observations:
• Left-hand limit (x→2⁻): Approaches 2
• Right-hand limit (x→2⁺): Approaches 2
• Since both one-sided limits agree, the limit exists and equals 2

Why other options are incorrect:
– A) 0: Not supported by the graph’s behavior near x=2
– B) 1: This is f(2), not the limit
– D: Incorrect because the limit does exist (both sides agree)

Remember: The limit describes the approaching behavior, not necessarily the function value at the point.

Question

On the following tables, which best reflects the values of a function g for which \(\lim_{x\rightarrow 7}g(x)=6\)?

A)

Table A showing function values

B)

Table B showing function values approaching 6

C)

Table C showing function values

D)

Table D showing function values
▶️ Answer/Explanation

Solution

Correct Answer: B

– Table B shows values approaching 6 from both sides of x=7:
  • As x→7⁻ (6.9, 6.99, 6.999): g(x) values approach 6 (5.8, 5.98, 5.998)
  • As x→7⁺ (7.1, 7.01, 7.001): g(x) values approach 6 (6.2, 6.02, 6.002)

Why other tables don’t satisfy the condition:
– Table A: Values approach different numbers from left (5) and right (7)
– Table C: Values don’t approach 6 from either side
– Table D: Values approach 6 from left but not from right

Key concept: For \(\lim_{x\rightarrow 7}g(x)\) to exist and equal 6, both one-sided limits must:
1) Exist
2) Equal 6
3) Table B is the only one satisfying both conditions

Question

Of the following tables, which best reflects the values of a function g for which \(\lim_{x\rightarrow 9}g(x)=5\)?

A)

Table A showing function values

B)

Table B showing function values

C)

Table C showing function values

D)

Table D showing values approaching 5 from both sides

▶️ Answer/Explanation

Solution

Correct Answer: D

Why Table D is correct:
Left approach (x→9⁻):
  • At x=8.9, g(x)=4.7
  • At x=8.99, g(x)=4.97
  • At x=8.999, g(x)=4.997
  → Clearly approaching 5
Right approach (x→9⁺):
  • At x=9.01, g(x)=5.005
  • At x=9.05, g(x)=5.025
  → Also approaching 5

Key concept: For \(\lim_{x\rightarrow a}g(x)=L\), we require:
1) \(\lim_{x\rightarrow a^{-}}g(x)=L\)
2) \(\lim_{x\rightarrow a^{+}}g(x)=L\)
3) Table D is the only option satisfying both conditions with L=5.

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