Integral : substitution & by parts of an exponential

Hello,

Quote:

Originally Posted by **Firstone**

Hi there, I was wondering if you could steer me ikn the right direction with an assignment question. It's a definite integral question.

Integral e^(sqrt{x}) dx (from 1 to 4)

It says i'm suppose to use substiution then integration by parts.

but I can't really see why I use substitution, it didn't makew anything easier.

I let u = sqrt{x}

I ended up with Integral e^(sqrt{x}) * 2du/sqrt{x}

I was just wondering if i did the substitution part right?

No, but you didn't substitute at all (Surprised)

Transform your integral : every x has to disappear. So as soon as you encounter , change it into u. If there was that you encounter, then and substitute too.

And then integrate by parts as recommended. Don't forget to either change the boundaries of the integral, either to substitute back u.

P.S. : please next time, post a new thread. It may be useful for some other people (Wink) (and my PM box is overwhelmed by all these messages lol!)