Question

Resolva os sistema:
a) x+y= -1
3x-y= 3

b) 5x-y= 4
2x-y= -5

c) x+2y= 7
4x-y= 10

d) x= 9-3y
3x+2y= 6

e) 5y-x= 5
2x-4= 3y

Answer 1

Resolva os sistema:

a)

x+y= -1

3x-y= 3 (+)

----------------

4x = 2 (:2)

2x = 1

x = 1/2

x + y = - 1

1/2 + y = - 1

y = - 1 - 1/2

2y/2 = (-1.2 - 1)/2

2y = ( -2-1)

2y = - 3

y = - 3/2

b)

5x-y= 4

2x-y= -5 (-1)

5x - y = 4

- 2x + y = 5 (+)

-------------------

3x = 9

x = 9/3

x = 3

5x - y = 4

5.3 - y = 4

15 - 4 = y

11 = y

Y = 11

c)

x+2y= 7

4x-y= 10 (2)

x + 2y = 7

8x - 2y = 20 (+)

9x = 27

x = 27/9

x = 3

X + 2y = 7

3 + 2y = 7

2y = 7 - 3

2y = 4

y = 4/2

y = 2

d)

x = 9 - 3y

3x+2y= 6

3x + 2y = 6

3.(9 - 3y) + 2y = 6

27 - 9y + 2y = 6

- 7y = 6 - 27

- 7y = - 21 (-1)

7y = 21

y = 21/7

y = 3

x = 9 - 3y

x = 9 - 3.3

x = 9 -9

x = 0

e)

5y-x= 5

2x-4= 3y

5y - x = 5

5y - 5 = x

x = 5y - 5

2x - 4 = 3y

2x - 3y = 4

2.(5y - 5) - 3y = 4

10y - 10 - 3y = 4

7y = 4 + 10

7y = 14

y = 14/7

y = 2

x = 5y - 5

x = 5.2 - 5

x = 10 - 5

x = 5