# Math Help - derivative help

1. ## derivative help

v = a(R - r)r^2

i need some help on finding the derivative...a is a constant

2. Originally Posted by mer1988
v = a(R - r)r^2

i need some help on finding the derivative...a is a constant
multiply out:

$v = a(R - r)r^2$

$\Rightarrow v = aRr^2 - ar^3$

now use the power rule