Math Calculus 1
posted by Anonymous .
Find the volume of the solid obtained by rotating y=3+2x-x^2, x+y=3 about the y-axis.
better integrate on x, since doing discs on y will need to separate the region into two pieces. So, using shells,
v = ∫[0,3] 2πrh dx
where r = x and h = (3+2x-x^2) - (3-x)
v = 2π∫[0,3] x((3+2x-x^2) - (3-x)) dx
= 2π∫[0,3] 3x^2-x^3 dx
= 2π(x^3 - x^4/4) [0,3]
= 27/2 π
If you would check my last 2 questions. I am just completely stumped.