Question

1. Resolva os sistemas.

Answer 1

a)

x + y = -1
3x - y = 3
---------------
4x = 2
x = 2/4
x = 0,5

valor de y:

x + y = -1
0,5 + y = -1
y = -1 - 0,5
y = -1,05

b)

5x - y = 4
2x - y = -5 . (-1)

5x - y = 4
-2x + y = 5
-----------------
3x = 9
x = 9/3
x = 3

valor de y:

5x - y = 4
5 . 3 - y = 4
15 - y = 4
-y = 4 - 15
-y = -11
y = 11

c)

x + 2y = 7
4x - y = 10 . 2

x + 2y = 7
8x -2y = 20
------------------
9x = 27
x = 27/9
x = 3

valor de y:

x + 2y = 7
3 + 2y = 7
2y = 7 - 3
2y = 4
y = 4/2
y = 2

d)

3x - 2y = 7
x + 2y = -16
------------------
4x = -9
x = -9/4
x = -2,25

valor de y:

3x - 2y = 7
3 . (-2,25) -2y = 7
-6,75 -2y = 7
-2y = 7+6,75
-2y = 13,75
y = 13,75/-2
y = -6,875