If g is inverse of f and $f'(x)=\frac{1}{1+x^n}$ then g'(x) equals
Answer & explanation
Correct answer: option 3
Since g is the inverse of f.
∴ fog(x) = x for all x
$\Rightarrow \frac{d}{d x}\{fog(x)\}=1 $ for all x
$\Rightarrow f'(g(x)) . g'(x)=1$
$\Rightarrow f'\{g(x)\}=\frac{1}{g(x)}$
$\Rightarrow \frac{1}{1+[g(x)]^n}=\frac{1}{g'(x)}$ $\left[∵ f'(x)=\frac{1}{1+x^n}\right]$
$\Rightarrow g'(x)=1+[g(x)]^n$