Help on this algebra question plz?

Sergeg Bubka of the ukraine is the current pole vault world record holder.A typical sergeg vault can be modled by y = -5/4(x-4)^2+20 determine the height of sergegs pole vault|||First rearrange the equation to the form ax^2+bx+c. Then complete the square to get it in the form (x+h)^2 +k, and k will be the maximum.