Question

{3x-y=15
x+4y=-21....... Qual a resoluçào?

Answer 1

{3x-y=15
{x+4y=-21
x=-21-4y
3(-21-4y)-y=15
-63-12y-y=15
-12y-y=15+63
-13y=78.(-1)
13y=78
y=78/13
y=6
x=-21-4y
x=-21-4.6
x=-21-24
x=-45
S={(-45, 6)}