# Homework Help: Improper Integrals / Antiderivatives.

1. Jul 9, 2009

### mortokr

1. The problem statement, all variables and given/known data
Evaluate each improper integral whenever it is convergent.

1. S 1-infinity 4 / x

2. S 4 - infinity 2/x^3/2

2. Relevant equations

3. The attempt at a solution

I'm having trouble with antiderivatives. I understand how to do them when the problem is like x^4 + x^2 + 3 or something but anytime they're in like a fraction form I get lost and the first step in improper integrals is finding the antiderivative.

2. Jul 9, 2009

### rock.freak667

well firstly do you know what is d/dx (lnx) gives?

Secondly 1/an = a-n

3. Jul 9, 2009

### mortokr

ln x = 1/x right?

So, 4/x would just be x2?

4. Jul 9, 2009

### rock.freak667

No. If you differentiate lnx with respect to x to get 1/x, and integration is the reverse of differentiation, then the integral of 1/x with respect to x gives what?