# Thread: volume by cylinderical shells

1. ## volume by cylinderical shells

Find the volume of the region bound by y=x^2 and y=x+2 revolved over the x-axis from -1 to 2 using the shell method

i tried dividing up the function into -sqrt(y) and sqrt(y) and x = y-2 but every time i try calculating the volume, i keep on getting the wrong answer, i know that the right answer is 14.4pi from the washer method. can anyone help me with this?

thanks alot

2. ## Re: volume by cylinderical shells

It is hard to say what you did wrong when you don't say what you did! I note that the "cylindrical shells", rotated about the x-axis, so radius y, will have "height" given by $\sqrt{y}- (y- 2)$ for y between 1 and 2 and by $\sqrt{y}- 0$ for y between 0 and 1. Did you take that into account?