Is This correct?

$\displaystyle (x+20)^4 (x-30)^3$

$\displaystyle u=(x+20)^4$

$\displaystyle du/dx = 4(x+20)^3$

$\displaystyle v=(x-30)^3$

$\displaystyle dv/dx=3(x-30)^2$

$\displaystyle dy/dx=v.du/dx + u . dv/dx$

$\displaystyle dy/dx = (x-30)^3 . 4 (x+20)^3 + (x+20)^4 . 3(x-30)^2$