∫x^4*e^(-x^2/2)/sqrt(2π)dx(-∞

∫x^4*e^(-x^2/2)/sqrt(2π)dx=∫-x^3*/sqrt(2π)de^(-x^2/2)
=-x^3*e^(-x^2/2)/sqrt(2π)|(-∞,+∞)+∫e^(-x^2/2)/sqrt(2π)dx^3
=∫3x^2e^(-x^2/2)/sqrt(2π)dx