The region bounded by the given curves is rotated about y = 7.
The lines are x = (y - 9)^2 and x = 4. I squared both functions and received (y-9)^4 and 16. Then I plugged in four for the first function to find my points (which I think would 7 and 11). So my integral was 16 - (y-9)^4 from 7 to 11. My answer was 51.2(pi). Should I have set different points or did I mess something else up?

Question

The region bounded by the given curves is rotated about y = 7.
The lines are x = (y - 9)^2 and x = 4.  I squared both functions and received (y-9)^4 and 16.  Then I plugged in four for the first function to find my points (which I think would 7 and 11).  So my integral was 16 - (y-9)^4 from 7 to 11.  My answer was 51.2(pi).  Should I have set different points or did I mess something else up?

anonymous · Answer

doesn't look like a right answer

anonymous · Answer

You are correct

anonymous · Answer

2pi ∫ (y-7) [4 - (y-9)^2] dy, from 7 to 11 should be correct

anonymous · Answer

and that should come out to be 128pi/3

anonymous · Answer

Alright, I think I got it, thanks