Question 81773
Given y = x^2 - 4x - 5

==>   y = x^2 - 4x + 4 - 4 - 5 [add and subtract 4 to make the first3 terms a perfect square]

==>   y = (x^2 - 4x + 4) - 9

==>   y = (x - 2)^2 - 9

This is of the form y = a(x-h)^2 + k where

       a = 1;   h = 2  and k = -9