Question

Resolva os sistemas.

a) { x+y=-3 b) { x+2y=12 c) -2x-6x=6
    3x+y=4         x+7y=-3        2x-9=-3

Answer 1

a)
{ X + Y = - 3..(-3)
{ 3X + Y = 4


-3X - 3Y = 9
..3X + Y = 4
_________
......- 2Y = 13

...... Y = - 13
.............____
.................2

X + Y = - 3

X + (-13/2) = - 3

X - 13 = - 3
.....___
........2

X = -3 + 13
..............___
................2

X = - 6 + 13
......_______
.............2

X = 7
......__
.......2

b)
{ X + 2Y = 12..(7)
{ X + 7Y = - 3..(-2)

.7X + 14Y = 84
-2X - 14Y = 6
___________
5X...........= 90

X = 90
.....___
.......5

X = 18


X + 2Y = 12

18 + 2Y = 12

2Y = 12 - 18

2Y = - 6

Y = - 6
......____
.........3

Y = - 2

c)
{ - 2X - 6Y = 6
{ ...2X - 9Y = - 3
____________
........... - 15Y = 3

........... Y = - 3
..................____..(÷3)
.....................15

Y = - 1
......___
.........5

- 2X - 6Y = 6
- 2X - 6 . -1......= 6
................___
..................5

- 2X + 6.....= 6
...........__
............5

- 2X = 6 - 6
.................__
...................5

- 2X = 30 - 6
...........______
................5

- 2X = 24
...........___
..............5

X = - 24
......____
.......5 x 2

X = - 24
.......____..(÷2)
..........10

X = - 12
.......____
...........5