Question

{x+y=3
{x-y=9 ???????

Answer 1

Olá,

x+y = 3
x-y = 9
-----------
x+x+y-y = 3+9
2x+0 = 12
2x = 12
x = 12/2
x = 6

x+y = 3
y = 3-x
y = 3-6
y = -3

Resposta:

(x,y) = (6,-3)