If the curves of f(x) and g(x) intersect x=a and x=b and if f(x)>g(x)>0 for all x on (a,b) then the volume obtained when the region bounded by the curves is rotated about the x-axis is equal to

Answer 1

using discs,
v = = ∫[a,b] π(R62-r^2) dx
where R=f(x) and r=g(x)

using shells, it gets a lot trickier, because we have to idea of the behavior of f and g in the interval.