integration by substitution

http://img413.imageshack.us/img413/6839/49887281.gif

**(a)** Let then and therefore . We get:

Both limits of integration in the new integral are 1, so the value of the definite integral is 0.

**(b)**

It is only zero when x=0. Jacobian become zero at (0,0) so it vanishes at this point.

**(c)** This is the part I'm really stuck on: from part (a) I know what to substitute for "dx" when I make the substitution . So I think this is what the question is asking for:

But expressions involving x should not appear in the new integrals. How do I get rid of the " "? Can anyone show me how to do this part?