# Math Help - Reverse the order of the integral

1. ## Reverse the order of the integral

Hello,
plz try to solve this question.
Thanks

2. Originally Posted by m777
Hello,
plz try to solve this question.
Thanks
This and your last question contained fairly easy integrals. If you are having trouble with them, please make sure try to point out what it is so we can help you.

In my (rather ugly) notation, we have:
Int[ Int[(1 - 6x^2*y) dy, -1, 1] dx, 0, 2]
vs.
Int[ Int[(1 - 6x^2*y) dx, 0, 2] dy, -1, 1]

The first is:
Int[ Int[(1 - 6x^2*y) dy, -1, 1] dx, 0, 2]

= Int[ [y - 3x^2*y^2, -1, 1], dx, 0, 2]

= Int[2 dx, 0, 2] = [2x, 0, 2] = 4

The second is:
Int[ Int[(1 - 6x^2*y) dx, 0, 2] dy, -1, 1]

= Int[ [x - 2x^3*y, 0 , 2] dy, -1, 1]

= Int[(2 - 16y) dy, -1, 1]

= [2y - 8y^2, -1, 1] = 4

-Dan