English

Lim X → 4 X 3 − 64 X 2 − 16

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Question

\[\lim_{x \to 4} \frac{x^3 - 64}{x^2 - 16}\] 

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Solution

\[\lim_{x \to 4} \left[ \frac{x^3 - 64}{x^2 - 16} \right]\]
\[ = \lim_{x \to 4} \left[ \frac{x^3 - 64}{x - 4} \times \frac{x - 4}{x^2 - 16} \right]\]
\[ = \lim_{x \to 4} \left[ \frac{x^3 - 4^3}{x - 4} \times \frac{x - 4}{x^2 - 4^2} \right]\]
\[ = 3 \left( 4 \right)^{3 - 1} \times \frac{1}{2 \left( 4 \right)^{2 - 1}}\]
\[ = \frac{3 \times 16}{2 \times 4}\]
\[ = 6\] 

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Chapter 29: Limits - Exercise 29.5 [Page 33]

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R.D. Sharma Mathematics [English] Class 11
Chapter 29 Limits
Exercise 29.5 | Q 8 | Page 33

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