suppose question is $$\frac{1}{(1+x)^3}$$ where $x<<1$ so answer will be $1-3x$ by binomial approximation. But if we do binomial approximation in denominator itself,answer will be $\frac{1}{(1+3x)}$
so basically is it like we rationalise the second answer and then $1>>9x^2$ so we get 1-3x or is there some other reason?