Hello. This is a calc question. For finding the volume of a solid revolving around x = -1 do you add -1 to the equation like this:

integral pi* [f(x) - 1]^2 dx

Thanks :)!

Question

Hello. This is a calc question. For finding the volume of a solid revolving around x = -1 do you add -1 to the equation like this:

integral pi* [f(x) - 1]^2 dx

Thanks :)!

anonymous · Answer

$x=-1$ is a vertical line, so if you wish to use the disk/washer method you must integrate with respect to $y$.

Let's check with an example. Let's have $f(x)$ be as shown in the picture, and you want the region bounded by this curve and the axes:
|dw:1402249309349:dw|