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BITSAT 2009
Exam
BITSAT
Year
2009
Subject
Mathematics
Chapter
Functions

BITSAT 2009 · Mathematics · Functions

The value of ( _ x arrow 0 ((4^x-1)^3)/( (x^2)/(4) (1+3 x))), is

The value of (\lim _{x \rightarrow 0} \frac{\left(4^x-1\right)^3}{\sin \frac{x^2}{4} \log (1+3 x)}), is

Options

  1. A(\frac{4}{3}(\ln 4)^2)
  2. B(\frac{4}{3}(\ln 4)^3)
  3. C(\frac{3}{2}(\ln 4)^2)
  4. D(\frac{3}{2}(\ln 4)^3)

Correct answer

B. (\frac{4}{3}(\ln 4)^3)

Step-by-step solution

(lim⁡x→0(4x−1)3sin⁡x24log⁡(1+3x)=lim⁡x→0(4x−1)3x3⋅(x/2)2sin⁡x2/4⋅3xlog⁡(1+3x)⋅43=43(log⁡e4)3⋅1⋅log⁡e(e)=43(log⁡e4)3.\begin{aligned} & \lim _{x \rightarrow 0} \frac{\left(4^x-1\right)^3}{\sin \frac{x^2}{4} \log (1+3 x)} \\ & =\lim _{x \rightarrow 0} \frac{\left(4^x-1\right)^3}{x^3} \cdot \frac{(x / 2)^2}{\sin x^2 / 4} \cdot \frac{3 x}{\log (1+3 x)} \cdot \frac{4}{3} \\ & =\frac{4}{3}\left(\log _e 4\right)^3 \cdot 1 \cdot \log _e(e)=\frac{4}{3}\left(\log _e 4\right)^3 . \end{aligned})
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