Hi Trevor,

You make the polynomial into a square by dividing the second term by 2 and squaring it.  22 divided by 2 is 11. And 11 squared is 121.  The completed square for the polynomial is then Z^2 + 22Z + 121.  Thus C must equal 121 for the polynomial to be a square.  This polynomial is the square of Z + 11 or (z + 11)^2.

To find the c term that completes the square, divide the coefficient on the z term by 2 and then square it

(22/2)²

11²

121

The c term that completes the square is 121