Question

Resolva os sistemas.
a) {×+y=-3
3×+y=1

b) {×+2y=12
3×-y=22

c) {-2×-6y=6
×+7y=-3

d) {5×-y=1
2×-3y=-10

e) {×+8y=-14
2×-9y=-3

f) {×-y=1
2×+y=4

g) {2×+3y=14
-×+5y=-7

Answer 1

a)
3x + 5y = 11
2x - y = 16     (5)

3x + 5y = 11
10x - 5y = 80 (+)
13x = 91
x = 91/13
x = 7

3x + 5y = 11
3.7 + 5y = 11
21 + 5y = 11
5y = 11 - 21
5y = - 10
y = -10/5
y = - 2
===========================
b) 
 x + y = 2      (2)
4x - 2y = 5

2x + 2y = 4
4x - 2y = 5
6x = 9
x = 9  (:3) =  3
      6  (:3)     2

x = 3
      2

x + y = 2
3 + y = 2
2

3 + 2y = 4
2y = 4 - 3
2y = 1
y = 1/2
c)
2x + 3y =  1    
2x + 5y = - 1 ( - 1)

  2x + 3y = 1
- 2x - 5y = 1 (+)
     - 2y = 2 ( - 1)
2y = - 2
y = -2/2
y = - 1

2x + 3y = 1
2x + 3.(-1) = 1
2x - 3 = 1
2x = 1 + 3
2x = 4
x = 4/2
x = 2

d) 
5x - y = 4
2x - y = - 5  ( - 1)

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

5x - y = 4
5x - 4 = y
5.3 - 4 = y
15 - 4 = y
11 = y
y = 11