- #1
nayfie
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Homework Statement
I'm having difficulty solving the following integral.
[itex]\int_{-\infty}^{\infty} x^{4}e^{-2\alpha x^{2}} \text{d}x[/itex]
Homework Equations
[itex]\int_{-\infty}^{\infty} e^{-\alpha x^{2}} \text{d}x = \sqrt{\frac{\pi}{\alpha}}[/itex]
[itex]\int_{-\infty}^{\infty} x^{2}e^{-\alpha x^{2}} \text{d}x = \frac{\sqrt\pi}{2\alpha^{\frac{3}{2}}}[/itex]
The Attempt at a Solution
I solved a very similar integral, however this one was much easier as I could use substitution quite easily. (In this case I let [itex]u = x^{2}[/itex] and [itex]\text{d}u = 2x\text{d}x[/itex]).
[itex]\int_{-\infty}^{\infty} x^{3}e^{-2\alpha x^{2}} \text{d}x[/itex]
(It turns out that the integral above is zero.)
The only difference in this new question is a factor of x, yet I have no idea how to approach it. Ideally I would want to find a way to manipulate this integral to be of a form that I know the solution (e.g the ones I've listed above).
Just need a point in the right direction. Any help would be greatly appreciated!