Let R be the region enclosed by the graphs of y=(64x)14 and y=x. How do you find the volume of the solid generated when region R is revolved about the x-axis?

1 Answer
Jun 30, 2017

64π3

Explanation:

First, plot the two graphs, shading the bounded region between them.

![Desmos.com](useruploads.socratic.org)

Second, recall the formula for solid of revolution about the x-axis

xfx0π(outer radius)2π(inner radius)2dx

The outer radius is the height from the x-axis to the outer most graph, or y=(64x)14

xfx0π((64x)14)2π(inner radius)2dx

The inner radius is the height from the x-axis to the inner most graph, or y=x

xfx0π((64x)14)2π(x)2dx

The lower limit of integration is the smallest x-value where the two curves meet, or x0=0. The upper limit of integration is the largest x-value where the two curves meet, or xf=4

40π((64x)14)2π(x)2dx

40π(64x)12πx2dx

40π8x12πx2dx

40π8x12dx40πx2dx

8π40x12dxπ40x2dx

163π[x32]40π3[x3]40

163π(4)32π3(4)3=64π3