Home / AP Calculus BC : 1.8 Determining Limits Using the Squeeze Theorem- Exam Style questions with Answer- MCQ

AP Calculus BC : 1.8 Determining Limits Using the Squeeze Theorem- Exam Style questions with Answer- MCQ

Question

Let \( f \) be a function of \( x \). The value of \( \lim_{x \to a} f(x) \) can be found using the squeeze theorem with the functions \( g \) and \( h \), where \( g(x) \leq f(x) \leq h(x) \) on the interval shown and \( \lim_{x \to a} g(x) = \lim_{x \to a} h(x) \). Which of the following could be graphs of \( f \), \( g \), and \( h \)?

A)

B)

C)

D)

▶️ Answer/Explanation
Solution
To apply the squeeze theorem, we need \( g(x) \leq f(x) \leq h(x) \) near \( x = a \), and \( \lim_{x \to a} g(x) = \lim_{x \to a} h(x) \).
The problem confirms this condition holds, with \( g \) and \( h \) converging to the same limit.
The graph in option D shows \( f \) squeezed between \( g \) and \( h \), both meeting at \( x = a \).
✅ Answer: D)
Question

The function \( g \) is given by \( g(x) = \frac{1}{x^{2} – 4x + 5} \). The function \( h \) is given by \( h(x) = \frac{2x^{2} – 8x + 10}{x^{2} – 4x + 6} \). If \( f \) is a function that satisfies \( g(x) \leq f(x) \leq h(x) \) for \( 0 < x < 5 \), what is \( \lim_{x \to 2} f(x) \)?

A) 0

B) 1

C) 2

D) The limit cannot be determined from the information given.

▶️ Answer/Explanation
Solution
To find \( \lim_{x \to 2} f(x) \), we evaluate the limits of \( g(x) \) and \( h(x) \) at \( x = 2 \):
\[ \lim_{x \to 2} g(x) = \frac{1}{2^{2} – 4(2) + 5} = \frac{1}{4 – 8 + 5} = \frac{1}{1} = 1 \]
\[ \lim_{x \to 2} h(x) = \frac{2(2)^{2} – 8(2) + 10}{2^{2} – 4(2) + 6} = \frac{8 – 16 + 10}{4 – 8 + 6} = \frac{2}{2} = 1 \]
Since \( g(x) \leq f(x) \leq h(x) \) and both \( g(x) \) and \( h(x) \) approach 1 as \( x \to 2 \), the Squeeze Theorem guarantees that:
\[ \lim_{x \to 2} f(x) = 1 \]
✅ Answer: B) 1
Question

The function \( f \) is defined for all \( x \) in the interval \( 3 < x < 6 \). Which of the following statements, if true, implies that \( \lim_{x \to 5} f(x) = 12 \)?

A) There exists a function \( g \) with \( f(x) \leq g(x) \) for \( 3 < x < 6 \), and \( \lim_{x \to 5} g(x) = 12 \).

B) There exists a function \( g \) with \( g(x) \leq f(x) \) for \( 3 < x < 6 \), and \( \lim_{x \to 5} g(x) = 12 \).

C) There exist functions \( g \) and \( h \) with \( g(x) \leq f(x) \leq h(x) \) for \( 3 < x < 6 \), and \( \lim_{x \to 5} g(x) = 11 \) and \( \lim_{x \to 5} h(x) = 13 \).

D) There exist functions \( g \) and \( h \) with \( g(x) \leq f(x) \leq h(x) \) for \( 3 < x < 6 \), and \( \lim_{x \to 5} g(x) = \lim_{x \to 5} h(x) = 12 \).

▶️ Answer/Explanation
Solution
The Squeeze Theorem states that if \( g(x) \leq f(x) \leq h(x) \) near \( x = a \), and \( \lim_{x \to a} g(x) = \lim_{x \to a} h(x) = L \), then \( \lim_{x \to a} f(x) = L \).
Option D satisfies these conditions with \( L = 12 \), so it implies \( \lim_{x \to 5} f(x) = 12 \).
Options A and B are insufficient (only one-sided bounds), and Option C does not guarantee convergence to 12.
✅ Answer: D)
Question

Find the limit: \(\lim_{x\rightarrow -\infty }\frac{\sin \Theta }{\Theta }\)

A) 0

B) −1

C) −∞

D) The limit does not exist.

▶️ Answer/Explanation
Solution
For any real number \(\Theta\), \(-1 \leq \sin \Theta \leq 1\). Therefore:
\[ \left| \frac{\sin \Theta}{\Theta} \right| \leq \frac{1}{|\Theta|} \]
As \(\Theta \rightarrow -\infty\), \(\frac{1}{|\Theta|} \rightarrow 0\). By the Squeeze Theorem:
\[ \lim_{\Theta \rightarrow -\infty} \frac{\sin \Theta}{\Theta} = 0 \]
✅ Answer: A) 0
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