So I have gotten the equation for the total surface area of a cylinder in term of its radius as:

$\displaystyle T.S.A.=2\pi r^2+\frac{810}{r}$

Where does one begin to even find the minimum surface area of this cylinder? I have to find the minimum surface area graphically on where itappearsto have minimum as well as through algebraic (optimisation) methods.

Help appreciated, thanks.