Calculating Integral of x^2-2x e^-x dx

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integral (x^2 - 2x) e^-x dx

Im just wondering if there's a fast way to calculate this integral or is the only way to do it by parts twice. The prof didnt show any work in the solution and went right to the solution. Am I missing something obvious?
 
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what is E?
 
sutupidmath said:
what is E?

eulers number (e)
 
I think your plan of using integration by parts is the way to go.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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