MCQ
$\lim\limits_{x \rightarrow 2} \frac{3^{x}+3^{3-x}-12}{3^{-x / 2}-3^{1-x}}$ is equal to
  • A
    $25$
  • $36$
  • C
    $49$
  • D
    $42$

Answer

Correct option: B.
$36$
b
$\lim _{x \rightarrow 2} \frac{3^{x}+3^{3-x}-12}{3^{-x / 2}-3^{1-x}} \Rightarrow \lim _{x \rightarrow 2} \frac{3^{2 x}-12.3^{x}+27}{3^{x / 2}-3}$

$=\lim _{x \rightarrow 2} \frac{\left(3^{x}-9\right)\left(3^{x}-3\right)}{\left(3^{x / 2}-3\right)}$

$=\lim _{x \rightarrow 2} \frac{\left(3^{x / 2}+3\right)\left(3^{x / 2}-3\right)\left(3^{x}-3\right)}{\left(3^{x / 2}-3\right)}$

$=36$

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