Hey,
I wanted to show (intended) that:
The right side is what I want to arrive at, i.e. I would like to continue from where I left off and arrive at the right-hand-side instead of "going backwards". I seem to be stuck !!?????
I know that; all I wanted you to notice is that you have arrived to the right side. It is just written in a different way. Just like you wrote the left side as an integral, you can do the same for the right side. You'll end up exactly with what your change of variable lead you to. Just one additional "hint" (not that you did it): , and take .