Question

............. x^2-12x-45=0

Answer 1

$x^{2} -12x-45=0\\D=144+180=324 \\ \sqrt{D} =18 \\ x_{1} = \frac{12+18}{2} = \frac{30}{2} =15 \\ x_{2} = \frac{12-18}{2} =- \frac{6}{2} =-3$