We sketch the upper and lower bounding curves:

The lower limit of integration is x = 0 (since the question says x ≥ 0).

Next, we need to find where the curves intersect so we know the upper limit of integration.

Equating the 2 expressions and solving:

2x2 = x + 1

2x2x − 1 = 0

(2x + 1)(x − 1) = 0

x = 1 (since we only need to consider x ≥ 0. This is consistent with what we see in the graph above.)

So with y2 = x + 1 and y1 = 2x2, the volume required is given by:

text[Volume]=pi int_0^1 [(x+1)^2-(2x^2)^2]dx

=pi int_0^1 [(x^2+2x+1)-(4x^4)] dx

=pi [(x^3)/(3)+x^2+x-(4x^5)/(5)]_0^1

=pi[(1/3 + 1+1 - 4/5)-(0)]

=pi[(5+30-12)/(15)]

=(23pi)/(15)

=4.817\ text[cm]^3

Here's an illustration of the volume we have found. A typical "washer" with outer radius y2 = x + 1 and inner radius y1 = 2x2 is shown.

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