# Homework Help: Integral problem

1. Jan 7, 2012

### Jalo

1. The problem statement, all variables and given/known data

(ignore what's written, it isn't important for the problem)

I'm studying integrals and I came across this solved example. However I can't understand where the minus of the integral came from came from.

2. Relevant equations

3. The attempt at a solution

The primitive of a f^p * f ' function is f^(p+1) / (p+1) Therefore it should be ln^2(x-1)/2 and not -ln^2(x-1)/2

Thanks

2. Jan 7, 2012

### Screwdriver

You could dispel any doubts by making a u-substitution. Try $u = 1 - x$ and see where that takes you.

3. Jan 7, 2012

### SammyS

Staff Emeritus
By the chain rule: $\displaystyle \frac{d}{dx}\ln(1-x)=\frac{1}{1-x}\frac{d}{dx}(1-x)=-\frac{1}{1-x}\,.$

So you have the anti-derivative of f^p * (- f ' ) .