Originally Posted by

**tastybrownies** Yeah, not sure why it says to use the washer method on the worksheet, maybe a mistake?

Well, took your advice and used the other method, A(x) = pi x^(2) change in x for the disks.

(-x^(2)+1)^(2) == x^(4)-2x^(2)+1, after integrating I ended up with

pi * (1/5(x)^(5)-2/3x^(3) )+1x/ integrated from -1 to 1,

I ended up with (8/5)- (-8/5) *pi = 16pi/15 or 3.35.... correct

For the other method, I did

(x^(2)+1)^(2) - (2-0x)^(2) ... no

after multiplying and integrating this, i ended up with the equation,

1/5x^(5) - 2/3x^(3) -3x/ integrated from -1 to 1,

I ended up with -6.93*pi= -21.78. Not sure if this should automatically be an absolute value because its volume.

Thank you again, I'm just trying to understand and wrap my mind around this!