the volume of a shell is 2πrh so sketch the region and assign the values as needed.
about the x-axis, using the symmetry of the region
v = 2∫[0,2] 2πrh dy
where r = y and h = 2-x = 2-(2-√(4-y))
v = 2∫[0,4] 2πy(√(4-y)) dy = 512π/15
check, using discs
v = ∫[0,4] πr^2 dx
where r = y = 4x-x^2
v = ∫[0,4] π(4x-x^2)^2 dx = 512π/15
Now, you try the others. Post your work if you get stuck.
Find the volume of the solid of revolution generated by revolving the region in the first quadrant bounded by the x-axis and the graph of
y = 4x − x2
about the following:
x axis:
y axis:
x=5:
y=4:
1 answer