Question

Решить систему уравнений { x^2- у^2= 72 { x+у=9

Answer 1

$\tt\displaystyle \left \{ {{x^2-y^2=72} \atop {x-y=9}} \right. \left \{ {{(x-y)(x+y)=72} \atop {x-y=9}} \right. \left \{ {{9(x+y)=72} \atop {x-y=9}} \right. \\\left \{ {{x+y=8} \atop {x-y=9}} \right. |+\left \{ {{2x=17} \atop {x+y=8}} \right. \left \{ {{x=8,5} \atop {y=-0,5}} \right.$

Ответ:$(8,5;-0,5)$