Volume of Solids of Revolution Question - Please Help

[nerdykitty28]

So I was working through one of the practice SACs that we have been given for SAC 4 and there was a question I was very confused about. Does anyone know how to go about solving this?

The question says "show that "

We are given and are told that the maximum volume is 1000L (something like that, I have left the paper at school and can't remember the whole question)

I know I have to rearrange y to get x and then substitute into the normal formula for volume of solids of revolution. But where did come from?!

[abeybaby]

Hey nerdykitty, If you manage to get hold of the whole question it would be considerably easier to help you. I can't seem to work out whats going on without the whole question...

[jia0020]

So I was working through one of the practice SACs that we have been given for SAC 4 and there was a question I was very confused about. Does anyone know how to go about solving this?

The question says "show that "

We are given and are told that the maximum volume is 1000L (something like that, I have left the paper at school and can't remember the whole question)

I know I have to rearrange y to get x and then substitute into the normal formula for volume of solids of revolution. But where did come from?!

So firstly the volume of revolution comes from: , that's where the y comes from

The maximum volume is when the derivative is equal to zero, so that's where the 1000 comes in.