# Math Help - Having trouble with simple integral :/

1. ## Having trouble with simple integral :/

It is the integral from 4 to 5 of t times square root of (t-4)

I tried integrating parts but did not come up with the correct answer. This is so simple I don't understand why I can't get this.

Thanks for the help.

2. ## Re: Having trouble with simple integral :/

Try the substitution u= t- 4. Then t= u+4 so [itex]t\sqrt{t- 4}= (u+4)u^{1/2}[/tex]. Don't forget to change the limits of integration: when t= 4, what is u? When t= 5, what is u?

3. ## Re: Having trouble with simple integral :/

Great! I did that substitution and it worked! I got the right answer. For learning purposes though, why couldn't I use integration by parts here?

Thanks.