# 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
one more question:how can someone delete a forum?

2. Recall that $\sqrt{a^3}-\sqrt{b^3}=\frac{a^3-b^3}{\sqrt{a^3}+\sqrt{b^3}}$.

3. You appear to be wanting to find, not the limit, but the derivative. And you have also posted this under "Algebra and PreAlgebra". Please to not post the same question in different places.