Thanks to everyone! This helps immensely, I really appreciate it. So for a function like (1 - x^2)^1/2 from 0 to 1, what I would do is make u = 1 - x^2, right? And then I would make it du/dx, giving me -2x..from here I'm less sure what to do. Do I try and solve for dx, or x, or what?