Question

Resolva os sistemas
A) x+y = 3
12x-9y=-20

B) 2x+y=7
5x-2y=-5

C) x-y=4
2x-4y=13

Answer 1

A) x-y=3
12x-9y=-20
x=3-y
12(3-y)-9y=-20
36-12y-9y=-20-36
-21y=-56
y=-56/-21
y=8/3
x=-5/3
b)x=1 y=5
c)x=5/-2