Can someone please help me complete this problem and understand it?

Find the volume of the solid created by rotating the region bounded by the curves below around the x-axis.

So far I have my work is as follows

The answer is

Please help

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- Dec 2nd 2008, 02:57 PMMcDieselVolume and Average Value
Can someone please help me complete this problem and understand it?

Find the volume of the solid created by rotating the region bounded by the curves below around the x-axis.

So far I have my work is as follows

The answer is

Please help - Dec 2nd 2008, 03:13 PMJameson
Your setup is almost right. You need to square the whole expression, meaning the 9 as well. That's where the 81 comes from. Bring the constants out and you have . The integral of 1/(x+5) is ln(x+5) and then all you do is plug in your bounds. The last part uses an identity that ln(a)-ln(b) = ln(a/b)