# Integration Help

1. Nov 8, 2007

### snoweangel27

I can't seem to figure this integral out
$$\int$$x^(1/2)*e^(-x) dx
from -$$\infty$$ to $$\infty$$

I have tried integrating by parts, but that didn't seem to do any good. Does anyone know a good way to start this problem?

2. Nov 8, 2007

### dextercioby

Y not make $$x=t^2$$ ?

3. Nov 9, 2007

### sennyk

Are we restricted to the reals? If so, then the limits of integration are not in the domain.

4. Nov 9, 2007

### D H

Staff Emeritus
Substituting x=t2 does not yield a Gaussian. As sennyk noted, the integration limits cannot be -infinity to infinity.

5. Nov 9, 2007

### Midy1420

break the integral into two parts one from -inf to 0 and then 0 to inf...if any of those two intregrals diverge then the whole thing diverges

6. Nov 9, 2007

### d_leet

The problem is more that the function isn't even defined on one of those intervals.