Find the volume of a trapezoid with vertices at (2,0), (2,2), (4,0), and (4,4); about the x-axis.

The trapezoid have vertices at (2,0), (2,2), (4,0), and (4,4)
and the rotation about the x-axis.
the points (2,0), (4,0) are located on the x-axis
calculate the function y = m x + c using the other vertices (2,2), (4,4)
by substituting in the function y
m = 1 , and  c =0
∴ y = x

The volume can be calculated using
 

∴
∴
∴