how do i do this

(5+6i)(5-6i)+14

$(5+6i)(5-6i)+14\\ =5^2 -(6i)^2+14\\ = 25-36i^2+14\\ =39-36i^2\qquad | \qquad \boxed{~i^2=-1~}\\ =39-36\cdot(-1)\\ =39+36\\ =75\\ \mathbf{(5+6i)(5-6i)+14 = 75}$