# Math Help - [SOLVED] find volume..

1. ## [SOLVED] find volume..

i cannot figure this out for the life of me.. find the volume of these functions using disk method:

y^2= x , x = 2y ; flip about the y - axis...

i m sure not getting that..

2. Originally Posted by Legendsn3verdie
i cannot figure this out for the life of me.. find the follow of these functions using disk method:

y^2= x , x = 2y ; flip about the y - axis...

i m sure not getting that..
look up the disk method, and make sure you understand how i set up the integral below

the volume is given by $V = \pi \int_0^2 [(2y)^2 - (y^2)^2]~dy$

3. So the area in question is the area bounded by the two curves $x = y^2; x = 2y$ and rotated around the y-axis. You can solve this by using washers or cylinders. If you use washers, the integral will be $\int _0 ^2 \pi(4y^2 - y^4) dy$.

4. ty

5. Just for fun, let's do it with shells and see if we get the same thing.

$2{\pi}\int_{0}^{4}x\left(\sqrt{x}-\frac{x}{2}\right)dx$

Also, from now on, anyone caught spelling 'pi' as
'pie' will be sent to a work camp.

6. Originally Posted by galactus
Also, from now on, anyone caught spelling 'pi' as
'pie' will be sent to a work camp.
haha, i caught that too. but i couldn't be bothered to point it out...yet again