# How do you find the volume of the solid #y=4-x^2# revolved about the x-axis?

##### 1 Answer

Use the disc method. The volume is

#### Explanation:

First, set

#0=4-x^2#

#x^2=4#

#x in {-2,2}#

So our bounds are

Next, use the disc method to find the volume (

#int_-2^2piy^2 dx = piint_-2^2(4-x^2)^2dx#

# = piint_-2^2(16-8x^2+x^4)dx#

#= pi [16x-8/3x^3+x^5/5]_-2^2#

#= pi (32-64/3+32/5)-pi(-32+64/3-32/5)#

#=512/15pi#

#=107.233#

*Final Answer*