# Math Help - first principle

1. ## first principle

Hi,can someone help me in finding the limit for (5x)^3/2 using first principle.
((5x+h)^3/2-(5x)^3/2)/h
This is all i got and then I am stuck on it.
Help would be greatly appreciated.
Thanx
One more
(3x+5)^3/2
2. Recall that $\sqrt{a^3}-\sqrt{b^3}=\frac{a^3-b^3}{\sqrt{a^3}+\sqrt{b^3}}$.