Question

How do you do $x^{2} -9x=15$

Answer 1

$x^2-9x=15\\x^2-9x-15=0\\a=1;\ b=-9;\ c=-15\\\Delta=b^2-4ac\to\Delta=(-9)^2-4(1)(-15)=81+60=141\\\\x=\frac{-b\pm\sqrt\Delta}{2a}\to x=\frac{9\pm\sqrt{141}}{2}$