Question

Resolva o seguinte sistema, algébrica e graficamente a) {× + 2y =1 {3× - 2y = 11 b) {×+ y=1 {×+2 y =4 c) {×+y = 3 {x-y=-1 d) {× - 2y =3 {2×-3y=5

Answer 1

a) x + 2y = 1

3x - 2y = 11

4x = 12

x = 12/4

x = 3

x + 2y = 1

3 + 2y = 1

2y = 1 - 3

2y = - 2

y = - 2/2

y = - 1

( 3, -1 )

b) x + y = 1     *(-1)

x + 2y = 4

- x - y = - 1

x + 2y = 4

y = 3

x + 2y = 4

x + 2(3) = 4

x + 6 = 4

x = 4 - 6

x = -2

( -2, 3 )

c) x + y = 3

x - y = - 1

2x = 2

x = 2/2

x = 1

x - y = - 1

1 - y = - 1

y = 1 + 1

y = 2

( 1, 2 )

d) x - 2y = 3         *(-2)

2x - 3y = 5

- 2x + 4y = - 6

2x - 3y = 5

y = - 1

2x - 3y = 5

2x - 3(-1) = 5

2x + 3 = 5

2x = 5 - 3

2x = 2

x = 2/2

x = 1

( 1, -1 )