I need SERIOUS HELP...integration by parts!!! 1. The problem statement, all variables and given/known data Integrate: x^3*e^x 2. Relevant equations 3. The attempt at a solution I have the answer in my book but I am not understanding why you have to repeat the integration 3 times... 1.) dv = e^x dx v = e^x u = x^3 du = 3x^2 S=integral sign lol S u*dv = uv - S v*du S x^3*e^3 = x^3*e^x - S 3x^2*e^x dx And now I have to do this 2 more times but I don't understand why and how I am supposed to know to do that?