1. Help with showing equations

Thanks!

2. The volume is $V={\pi}r^{2}h$

Since $h=2-2r$, we can sub it in the volume formula:

$V={\pi}r^{2}(2-2r)=2{\pi}r^{2}-2{\pi}r^{3}$

Now maximize.

3. Re: Updated!!!!!!!

Thanks very much for your help, i understand now!