rotation of region bounded by x^2 and y = 1 about y=1

[ihatecalc]

the problem states:

find the volume of the solid generated by revolving the region bounded by the parabola y=x^2 and the line y=1 about:

a) y=1

b) y=-1

the answer for A is 16pi/15, but i got 8pi/15

and the answer for B is 64pi/15, but i got 17pi/15.

can someone please show me how to go about doing these? why am i getting the wrong answers??

 

[stapel]

why am i getting the wrong answers??

Please reply showing all of your work and reasoning, so that we may provide the requested analysis.

Thank you.

Eliz.

 

[tkhunny]

the answer for A is 16pi/15, but i got 8pi/15

I didn't look at the problem, but it seems prudent to ask if you used both sides of the y-axis.

 

[galactus]

the problem states:

find the volume of the solid generated by revolving the region bounded by the parabola y=x^2 and the line y=1 about:

a) y=1

\(\displaystyle \L\\{\pi}\int_{-1}^{1}(x^{2}-1)^{2}dx\)

[quote:152nvgtp]b) y=-1

[/quote:152nvgtp]

\(\displaystyle \L\\{\pi}\int_{-1}^{1}(-1-1)^{2}-(x^{2}+1)^{2}dx\)