let
then
so you have:
I'm doing so much math I think I got a blank on the substitution method for solving integrals.
My work is scanned in the attachment. I think I'm on the right track but there is something I'm forgetting because I'm stuck in a loop.
I can follow these steps and understand them except the part where we get to the last line and we introduce ln. I know 1/u = ln|u| but where does the numerator 3x^2dx go?
Edit: Also, the integral has limits of integration 3 and 4, what do we do with this? Normally when I see limits like this I apply a formula F(b) - F(a), would this be the step after the final step shown above?