Question

1)resolva os sistemas pelo método da substituicao a)x+y=4/3x+y=28

Answer 1

$\left \{ {{x+y=4} \atop {3x+y=28}} \right. \\\\x=4-y\\3(4-y)+y=28\\12-3y+y=28\\-3y+y=28-12\\-2y=16\\-y=8\\y=-8\\\\x=4-(-8)\\x=4+8\\x=12$

Answer 2

x+y=4
3x+y=28

y=4-x

3x+4-x=28

2x=28-4

2x=24

x=24/2

x=12

y=4-x

y=4-12

y=-8


s={12,-8}


espero ter ajudado!

boa tarde!!