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**Boris B** Okay, pondering hasn't helped. I can't figure out why you chose to multiply by 3/3 instead of 14/14 or something. Would your solution be different if e were a different number? Is your solution an example of U substitution?

Whether or not it is, does anyone know a place on the web that explains U substitution really simply, in as many steps as necessary? My book on the subject is *literally* an idiot's guide ... it blathers cheerfully about how you should "use your *u* and *du* expressions to replace parts of the original integral" which is little help.

I'm looking for something which will always define what u and du are in the specific example, as well as something that will explain if and when du is an actual factor to be multiplied, and when it just sits there on the end of the integration expression the way dx does (AFAIK, you don't multiply any dxs before, during, or after integrating ... the Hacker's tutorial seemed to back me up on this).