Evaluate the following:
`int(1+x)e^xdx`

Explanation

`int(1+x)e^xdx`
[Choolse 1+x as first and `e^x`
as second function]
=`(1+x).e^x-int1.e^xdx`
=`(1+x)e^x-e^x+C=xe^x+C`