Problem

Find the volume of the solid formed by rotating the region enclosed by
x=0,x=1,y=0,y=9+x2
about the y-axis.

Answer

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Answer

Adding these together gives the total volume of the solid as 192π cubic units.

Steps

Step 1 :First, we need to understand that the solid is formed by rotating the region enclosed by the given equations about the y-axis. This means that the solid is a series of cylindrical shells, each with a radius equal to the x-coordinate, a height equal to the difference between the upper and lower y-values, and a thickness of dx.

Step 2 :The volume of each cylindrical shell is given by the formula 2πxhdx, where x is the radius, h is the height, and dx is the thickness.

Step 3 :In this case, the radius x ranges from 0 to 1, the height h is given by the equation 9+x2, and the thickness dx is a small change in x.

Step 4 :We can find the total volume of the solid by integrating the volume of each cylindrical shell from x=0 to x=1. This gives us the integral 012πx(9+x2)dx.

Step 5 :We can simplify this integral by distributing the 2πx to get 0118πx+2πx3dx.

Step 6 :We can then evaluate this integral by finding the antiderivative of the integrand and evaluating it at the limits of integration. The antiderivative of 18πx is 9πx2, and the antiderivative of 2πx3 is 12πx4.

Step 7 :Evaluating these at the limits of integration gives (9π(1)2+12π(1)4)(9π(0)2+12π(0)4)=9π+12π.

Step 8 :Adding these together gives the total volume of the solid as 192π cubic units.

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