Hi can some more knowledgeable than I please check my work?

Calculate the derivative using the differentation rules

a)

f(x) = (4x^4 - (2/5)x^3)^1/4

f'(x) = 1/4 (4x^4 -2/5x^3)^-3/4 (16x3-(6/5)x^2)

b)

f(x) = e^-5x + 3tan4x)^5

f'(x) = 5(e^-5x+3tan4x)4(-5e^-5x+12sec^2)

c)

f(x) = √(cosx + √x^7)

f'(x) = 1/2 (cosx + x^7/2)^-1/2 (-sin + (7/2)x^5/2)

I appreciate your help

Thanks