Question

Find derivative of f(x)=9x^20/15x^28

Answer 1

First simplify the function

$f(x) = \cfrac{9x^{20}}{15x^{28}} = \cfrac35x^{-8}$

Then find derivative

$f'(x) = (\cfrac35x^{-8})' = \cfrac{3}{5}\cdot (-8)x^{-9} = -\cfrac{24}{5}x^{-9}$