Friday, 1 September 2017

integration - Calculus Question: Improper integral displaystyleintinftyinftyx2exe2xdx



I am curious about evaluation of the following integral

x2exe2xdx
Is it possible to evaluate it? This not my homework but I will share my attempt. I tried standard technique, integration by part but without any success. I also couldn't find any suitable substitution. The integral seems as if it were evaluating the expected value or moment generating function of a certain distribution but I couldn't find any pdf like the integrand in my textbook table.


Answer



Hint: Show that eaxex dx=Γ(a).  Then, after substituting x=2t, differentiate twice with



regard to a, and let a=12.


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