.I need help again, after pondering this for a while

If a and b are positive numbers, prove that

I think I should make and , then I get:

This is almost correct, but after the substitution , the integral limits get reversed: , so all is fine but the last integral's lower limit is 1 and the upper one is 0.

Tonio

However, I have been stuck here for a while.

I don't know how to get rid of the negative nor how to substitute in back x without messing it back up.