Question

PRECISO DA RESPOSTA DE
X+Y=1
X-2Y=1

Answer 1

Subtraia uma conta da outra:

$x+y=1\\-\\x-2y=1\\\\x-x+y-(-2y)=1-1\\\\3y=0\\\\y=0\\\\x+y=1\\\\x+0=1\\\\x=1$