MCQ
$\lim _{x \rightarrow 0}\left(\frac{15^x-3^x-5^x+1}{\sin ^2 x}\right)=$
  • A
    $\log 15$
  • B
    $\log 3+\log 5$
  • $\log 3 . \log 5$
  • D
    $3 \log 5$

Answer

Correct option: C.
$\log 3 . \log 5$
(C) $\log 3 . \log 5$
Hint:
$\lim _{x \rightarrow 0}\left(\frac{15^x-3^x-5^x+1}{\sin ^2 x}\right)$
$=\lim _{x \rightarrow 0}\left[\frac{\left(5^x-1\right)\left(3^x-1\right)}{x^2} \times \frac{x^2}{\sin ^2 x}\right] $
$\because x \rightarrow 0, x \neq 0$
$\therefore x^2 \neq 0$
$=\log 3 \cdot \log 5$

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