Question

A= x-y=3
x-3x=6



b=x-y=3
2x-2y=6

Answer 1

$a) \left \{{{x-y=3}(1) \atop {x-3x=6}(2)} \right. \\ de,(2),temos \\ -2x=6 \\ x =-3 \\ -3-y=3 \\ y=-6 \\ b) \left \{ {{x-y=3}(1) \atop {2x-2y=6}(2)} \right. \\ multiplicando,(1),por 2,temos \\ 2x-2y=12\\ fazendo (1)-(2),temos, \\ 2x-2y-2x+2y=3-12 \\ 0x-0y=-9 (sistema,impossivel)$