MCQ
If $f$ is strictly increasing function, then $\mathop {\lim }\limits_{x \to 0} \frac{{f({x^2}) - f(x)}}{{f(x) - f(0)}}$ is equal to
  • A
    $0$
  • B
    $1$
  • $-1$
  • D
    $2$

Answer

Correct option: C.
$-1$
c
(c) $\mathop {\lim }\limits_{x \to 0} \frac{{f({x^2}) - f(x)}}{{f(x) - f(0)}}$,    $\left( {\frac{0}{0} \,\, {\rm{form}}} \right)$

$ = \mathop {\lim }\limits_{x \to 0} \frac{{2xf'({x^2}) - f'(x)}}{{f'(x)}}$,       (using $L'$  Hospital's rule)

$ = - 1 + \mathop {\lim }\limits_{x \to 0} \frac{{2xf'({x^2})}}{{f'(x)}} = - 1,f'(0) \ne 0,\,$

as $f$ is strictly increasing.

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