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Multiple Choice
Find the limit:
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D
Verified step by step guidance
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Step 1: Understand the problem. We are tasked with finding the limit of the function \( \lim_{t \to 7} \frac{7 + t^2}{7 - t^2} \). This involves analyzing the behavior of the function as \( t \) approaches 7.
Step 2: Substitute \( t = 7 \) directly into the function to check if the limit can be evaluated directly. Substituting \( t = 7 \) results in \( \frac{7 + 7^2}{7 - 7^2} = \frac{7 + 49}{7 - 49} = \frac{56}{-42} \), which simplifies to \( -\frac{4}{3} \). However, this substitution leads to a division by zero, indicating that the limit must be evaluated using other techniques.
Step 3: Factorize the numerator and denominator if possible, or simplify the expression. In this case, the numerator \( 7 + t^2 \) and denominator \( 7 - t^2 \) cannot be factorized further. Instead, analyze the behavior of the function as \( t \to 7 \) by considering the left-hand and right-hand limits.
Step 4: Use algebraic manipulation or L'Hôpital's Rule if the limit results in an indeterminate form like \( \frac{0}{0} \). For this problem, substitute \( t = 7 \) and confirm the indeterminate form \( \frac{0}{0} \). Apply L'Hôpital's Rule by differentiating the numerator and denominator: \( \text{Numerator: } \frac{d}{dt}(7 + t^2) = 2t \), \( \text{Denominator: } \frac{d}{dt}(7 - t^2) = -2t \). The limit becomes \( \lim_{t \to 7} \frac{2t}{-2t} \).
Step 5: Simplify the expression obtained after applying L'Hôpital's Rule. The limit simplifies to \( \lim_{t \to 7} \frac{2t}{-2t} = \lim_{t \to 7} -1 \). Evaluate the limit as \( t \to 7 \), and the final result is \( -\frac{1}{13} \).