stuck on simple facotring step(?) of differential equations question

[cujo9k]

the problem was dy/dx=2x-y

Anyways, the solution went like this:
dy/dx+y=2x
Multiply entire equation by integrating factor of e^x
e^(x) * (dy/dx)+e^x*y=e^x*2x

This is where I got confused:
Re-write equation as:
d/dx [y*e^x] = 2x*e^x

Could anyone explain the factoring to me:
e^(x) * (dy/dx)+e^x*y becomes d/dx [y*e^x]

Graphically it looks like this:
View attachment 3679 or http://www.wolframalpha.com/input/?i=d/dx[y*e^x]%3De^x*%28dy%2Fdx%29%2Be^x*y

Thanks

edit:
Nevermind.. figured it out. Apparently with the method of integrating factors, you have to multiply d/dx[y*integrating factor] = RHS. I must've missed the y*IF steps in the textbook. my bad.

feel free to close it ><