r = -5x^2 + 73x

Can someone show me the steps to complete the square for that equation? I don't really understand them.

-5x^2 + 73x

-5(x^2 - 73/5 x)
-5(x^2 - 73/5 x + (73/10)^2) + 5(73/10)^2
-5(x - 73/10)^2 + 5329/20