Question

Решите систему уравнений
   {х^2-y^2=72
   {x+y=9

Answer 1

$(x-y)(x+y)=72 9(x-y)=72 x+y=9 x=9-y 9(9-y-y)=72$

$9-2y=8 -2y=-1 y=0,5 x=9-0,5=8,5$