Originally Posted by

**Marconis** For the first example you provided: I can already tell that taking the derivative of (x^2 + 5x -11) would give you (2x + 5). So, in my head I'd pick that to substitute. I'd then go to take the derivative of it: u=(x^2 + 5x -11). Solving du/dx gives you: du/dx=2x+5. Solving for du, you get du=2x+5dx. Ah ha! See that above. So, (2x+5) simply becomes du. Finding the antiderivative of, (u)^5du. Brings (u^6/6) + C which gives, (x^2 + 5x -11)^6 / 6 + C. Am I correct? This is how I learned it (so I hope I did it correctly). I am curious why the du vanishes?