SOLVED find the volume of the curves rotated about the x-axis

Nov 2009
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the endpoint comes -1 and 1

and I am taking the integral of ((9/8)-x^2)-(x^2/8)....and then multiplyig by 2pi.

the final answers come 3pi.

Any help

thanks
 

skeeter

MHF Helper
Jun 2008
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method of washers ...

\(\displaystyle \displaystyle V = \pi \int_a^b [R(x)]^2 - [r(x)]^2 \, dx\)
 
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skeeter

MHF Helper
Jun 2008
16,217
6,765
North Texas
so its like this
with end points of -1 and 1
second term in the integrand should be \(\displaystyle \left(\frac{x^2}{8}\right)^2\) if what you posted originally is correct ...

\(\displaystyle \frac{x^2}{8} \ne \frac{1}{8x^2}\)

also ... limits of integration?
 
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