Question

resolvam cada sistema abaixo pelo método que preferir:

A){2x+5y=9
{-x+7y=5

B){-x+y=5
{-3x-y=7

C){2x+y=8
{-x+y=-4​

Answer 1

A) {2x+5y=9

{-x+7y=5

-x + 7y = 5 . 2

-2x + 14y = 10

2x + 5y = 9

+

-2x + 14y = 10

0 + 19y = 19

19y = 19

y = 19/19

y = 1

2x + 5y = 9

2x + 5 . 1 = 9

2x + 5 = 9

2x = 9 - 5

2x = 4

x = 4/2

x = 2

B) {-x+y=5

{-3x-y=7

-x + y = 5

+

-3x - y = 7

-4x + 0 = 12

-4x = 12

x = 12/-4

x = -3

-x + y = 5

-(-3) + y = 5

3 + y = 5

y = 5 - 3

y = 2

C) {2x+y=8

{-x+y=-4

-x + y = -4 . 2

-2x + 2y = -8

2x + y = 8

+

-2x + 2y = -8

0 + 3y = 0

3y = 0

y = 0/3

y = 0

2x + y = 8

2x + 0 = 8

2x = 8

x = 8/2

x = 4