Question 4

Mathematics Limit of Functions Hard

\(\lim _{{x}\rightarrow1}\frac{{x}^4-1}{x-1}=\lim _{{x}\rightarrow k}\frac{{x}^3-{k}^3}{{x}^2-{k}^2}\), then find k

(A) 8/3
(B) 4/3
(C) 2/3
(D) 1
✓ Correct Answer: Option A Verified Solution

📘 Step-by-Step Solution & Detailed Explanation:

Let's carefully go through the solution using L'Hopital's Rule: \[\] The given problem is: \[ \lim _{x \rightarrow 1} \frac{4 x^3}{1} = \lim _{x \rightarrow k} \frac{3 x^2}{2x} \] We need to evaluate both limits. \[\] Left-hand side: \[\] We evaluate the limit as \(x \to 1\): \[ \lim _{x \rightarrow 1} \frac{4 x^3}{1} = 4 \times 1^3 = 4 \] Right-hand side: \[\] We now consider the second expression: \[ \lim _{x \rightarrow k} \frac{3 x^2}{2x} \] Simplify the expression: \[ \frac{3 x^2}{2x} = \frac{3x}{2} \] Thus, the limit becomes: \[ \lim _{x \rightarrow k} \frac{3 x}{2} = \frac{3k}{2} \] Equating both sides of the problem: \[ 4 = \frac{3k}{2} \] Now, solve for \( k \): \[ k = \frac{8}{3} \]

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