# Homework Help: Definite integration

1. Aug 10, 2007

### cd246

1. The problem statement, all variables and given/known data
integration 9_0 c/x^3 dx. the answer is (3/8)c.

2. Relevant equations
just distrib. then plug in the #'s

3. The attempt at a solution
=cx^-3
= (cx^-2)/-2=c/-2x^2
I know it has something to do with distribution.

Last edited: Aug 10, 2007
2. Aug 10, 2007

### G01

$$\int^9_0 \frac{c}{x^3}dx$$

If this is the case, I agree with your answer. When I evaluate the integral at the bounds I do not get the answer you stated. I get -c/162 as an answer. Are you sure that is correct?

Last edited: Aug 10, 2007
3. Aug 10, 2007

### cd246

My apologies, it is 2_1 not 9_0

4. Aug 10, 2007

### G01

Ahh if that is the case, then I do get (3/8)c as the answer. Were the bounds your problem, or is there something else?

5. Aug 10, 2007

### cd246

that was pretty much it. did u put x^3 on top? or did you left the x^3 on the bottom? Because i believe that was my problem on this one.

6. Aug 10, 2007

### G01

I think it is good practice to write any fraction of c/x^n as cx^-n. I think it makes many problems look less complicated. So, yes, if this is what you mean, I did "put the x^3 on top."

7. Aug 10, 2007

### cd246

ok i got it now. thanx

8. Aug 10, 2007