Question

решите систему уравнений х-у=7 ху=-12

Answer 1

$left { {{x-y=7} atop {xy=-12}} right.$
$left { {{x=7</var><var>-y} atop {xy=-12}} right.$

y(7-y)=-12
7y-y²=-12

y²-7y-12=0

D=49-4·12=1

y₁=7+1/2=4

y₂=7-1/6=3

x₁=7-4=3

x₂=7-3=4

$left { {{x_1=3} atop {y_1=4}} right. left { {{x_2=4} atop {y_2=3}} right.$