I was just messing around, and wondering is what I've done valid. I made this up myself - but that's not to say it doesn't already exist. It has to do with series expansions.
Let W be an integration from 0 to x.
We^x = e^x -1
1 = e^x - We^x
1 = (1-W)e^x
1/(1-W) = e^x
Using this we can get that e^x = (1 + W + W^2 + W^3 + ... + W^n), which is (1 + W + W^2/2! + W^3/3! + ... + W^n/n!)
Is this a valid form of getting a series expansion? Is there a problem somewhere? And, is there a name for it?