# Math Help - Math C Question on 'Volumes of Revolution'

1. ## Math C Question on 'Volumes of Revolution'

Ok so I have the two coordinates (0,3) and (2,7)
The line that runs through them is y=2x+3
How do I find the volume created by rotating the line around the x axis..
In other words, I will be using volumes of revolution.

However, I have only bee taught on this how to just find the volume of a straight line only using one coordinate. Would it work the same or would I need to use both coordinates? Would the limits be from 0 to 7? and then intergrating 4x^2+12x+9 and multiplying it by pie?

Many thanks to those who reply

2. ## Re: Math C Question on 'Volumes of Revolution'

Originally Posted by BryannaAllan
Ok so I have the two coordinates (0,3) and (2,7)
The line that runs through them is y=2x+3
How do I find the volume created by rotating the line around the x axis..
In other words, I will be using volumes of revolution.
If you want to use calculus then
$\int_0^2 {2\pi {r^2}dx}$ where $r=(2x+3)$.

However, simple algebra will work. It is the difference of the volumes of two cones.