Z^2 = (2 + sqrt(7))^2 + (2 - sqrt(7))^2Z^2 = 4 + 4sqrt(7) + 7 + 4 - 4sqrt(7) + 7Z^2 = 15 + 11Z^2 = 26
Z^2 = (2 + sqrt(7))^2 + (2 - sqrt(7))^2
Z^2 = 4 + 4sqrt(7) + 7 + 4 - 4sqrt(7) + 7
Z^2 = 15 + 11
Z^2 = 26