Question

Resolva os sistemas:

1) 2x + 3y= 4
X - y = 2


2) x + y + z = 6
2x + y -Z = 1
3x -y + z = 4

Answer 1

$\left \{{2x+3y=4} \atop {x-y=2}(*-2)} \right. \\ \left \{{{2x+3y=4} \atop {-2x+2y=-4}} \right. \\ 5y=0 \\ y=-5$
$x-y=2 \\ x-(-5)=2 \\ x+5=2 \\ x=2-5 \\ x=-3$
$\left \{ {{x+y+z=6} \atop {2x+y-z=1}} \atop {3x-y+z=4}} \right. \\ \left \{ {{x+y+z=6} \atop {2x+y-z=1}} \right. \\ 3x+2y=7 \\ \left \{ {{x+y+z=6 (*-1)} \atop {3x-y+z=4}} \right. \\ \left \{ {{-x-y-z=-6} \atop {3x-y+z=4}} \right. \\ 2x-2y=-2$
$\left \{ {{3x+2y=7} \atop {2x-2y=-2}} \right. \\ 5x=5$
$\left \{ {{x+y+z=6} \atop {3x+2y=7}}\atop{5x=5}} \right. \\ x=1 \\ 3*1+2y=7 \\ 3+2y=7 \\ 2y=7-3 \\ y=4/2 \\ y=2 \\ x+y+z=6 \\ 1+2+z=6 \\ z=6-3 \\ z=3$