I am having a few problems with two derivative problems.

The first problem is to find the derivative of sqr(1-25x^2)arcos(5x) and simplify if possible. I havent got the right answer after many tries i assumed you needed to use the product rule to compute this derivative.

The next problem is to find the tangent line at the point (-3sqr(3),1) for the curve x^(2/3) + y^(2/3) = 4.

If anyone could show me how to do this it would be much appreciated.