Let \( f:\mathbb{R}\to \mathbb{R} \) be defined as \( f(x)=x^3+x-5 \).If \( g(x) \) is a function such that \( f(g(x))=x \), \( \forall 'x'\in \mathbb{R} \) then \( g'(63) \) is equal to ________________.
\( \dfrac{1}{49} \)
\( \dfrac{3}{49} \)
\( \dfrac{43}{49} \)
\( \dfrac{91}{49} \)