1. ## Integration : Volumes bounded by the y-axis (Help Please)

If anyone can help me understand how to do this question, it would be greatly appreciated.

'A bird bath is made by rotating the area bounded by the parabola
y= 1/3x^2, the y-axis and the line y=5. What volume of water does the bird bathhold when it is full?'

$\displaystyle \frac{x^2}{3}=5$
$\displaystyle x=\mp \sqrt{15}$ now use Washer method
$\displaystyle \int_{-\sqrt{15}}^{\sqrt{15}} \pi \left(25-\frac{x^2}{3}\right)^2 dx$