Question

 {x-y=9;

 {xy=-14; решить систему уравнений подробно)

Answer 1

$left { {{x-y=9} atop {xy=-14}} right. \ \ left { {{x=y+9} atop {xy=-14}} right.\ \ (y+9)y=-14\ \ y^2+9y=-14\ \ y^2+9y+14=0\ \ D=81-56=25\ \ y_{1}=frac{-9+5}{2}=-2\ \ y_{2}=frac{-9-5}{2}=-7\ \ x_{1}=-2+9=7\ \ x_{2}=-7+9=2$