Question

sistema de equações do 1 grau com duas incognitas:
a) {x+y=20
{x-y=8
b) {3x-y=18
{x+y=10
c) {2x+y=-3
{x-3y=-26

Answer 1

a) 2x = 28
    x = 28/ 2
    x = 14
---
14 + y = 20
y = 20 - 14
y = 6
--------
b) 4x = 28
    x = 28/4
    x = 7
---
7 + y = 10
y = 10 - 7
y = 3
--------
c) 7y = 49
    y = 49/7
    y = 7
---
2x + 7 = -3
2x = -3 -7
2x = -10
x = -10/2
x = -5
--------
prontinho

Answer 2

a) {x+y=20
{x-y=8
2x=28
x=28/2
x=14
x-y=8
14-y=8
-y=8-14
-y=-6.(-1)
y=6
S={(14, 6)}
b) {3x-y=18
{x+y=10
x=10-y
3(10-y)-y=18
30-3y-y=18
-3y-y=18-10
-4y=8.(-1)
4y=-8
y=-8/4
y=-2
x=10-y
x=10-(-2)
x=10+2
x=12
S={(12, -2)}
c) {2x+y=-3
{x-3y=-26
x=-26+3y
2(-26+3y)+y=-3
-52+6y+y=-3
6y+y=-3+52
7y=49
y=49/7
y=7
x=-26+3y
x=-26+3.7
x=-26+21
x=-5
S={(-5, 7)}