Question

equações do 1 grau com duas incógnitas (com a conta por favor):

1) {3 x+4 y=49
{x+3 y=33

2) {6 x+3 y=54
{x+4 y=16

3) {x+2 y=15
{3 x+y=15

4) {8 x+y=2
{14 x+y=-4

Answer 1

1) 3x+4y=49
x+3y=33    <~~~ x=33-3y
3(33-3y)+4y=49
99-9y+4y=49
-5y=49-99
-5y=50
y=10
x=33-3y
x=33-3.10
x=33-30
x=3

2) 6x+3y=54
x+4y=16    <~~~ x=16-4y
6(16-4y)+3y=54
96-24y+3y=54
-21y=54-96
-21y=-42
y=2
x=16-4y
x=16-4.2
x=16-8
x=8

3) x+2y=15~<~~  x=15-2y
3x+y=15
3(15-2y)+y=15
45-5y=15
-5y=-30
y=6 
x=15-2y
x=15-12
x=3

4) 8x+y=2   <~~ y=2-8x
14x+y=-4
14x+2-8x=-4
14x-8x+2=-4
6x=-4-2
x=-1
y=2-8x
y=10