There are three problems where I had difficulty answering:

the first is (sqrt) ((x-1)/(x^5))

The first thing i did was distribute the x^5 and got:

(sqrt)(x^(-4) - x^(-5))...

I gave the value (x^(-4) - x^(-5)) for u and got:

du = -4x^(-3) + 5x^(-4). I am not sure if I am doing this right so far.

THe answer is (2/3)(1-(1/x))^(3/2) + C

The second is dz/(1 + e^z)

I used (1 + e^z) to equal u and du = e^z.

This is where I got confused.

the answer was: z - ln(1+e^z) + C... the z part baffled me more.