Question

2o pontos 

a)x+y=15
  x-y=1
 
b)2x+y=1
  -x+3y=8

c)3x+y=12
  x-5y=4

d)2x+3y=11
  x+5y=16

Answer 1

A) x+y = 15
x = 15-y - Substituindo y=7
x = 15-7
x = 8*

x-y = 1
15-y-y = 1
-2y = 1-15
-2y = -14(-1)
y = 14/2 = 7*

B)-x+3y = 8
-x = 8-3y(-1)
x = -8+3y - Substituindo y=2,42
x = -8+3(2,42)
x = -8+7,26
x = -0,74*

2x+y = 1
2(-8+3y)+y = 1
-16+6y+y = 1
7y = 1+16
7y = 17
y = 17/7 = 2,42*

C)x-5y = 4
x = 4+5y - Substituindo y=0
x = 4*

3x+y = 12
3(4+5y)+y = 12
12+15y+y = 12
16y = 12-12
y = 0*

D)x+5y = 16
x = 16-5y - Substituindo y=3
x = 16-5(3)
x = 16-15
x = 1*

2x+3y = 11
2(16-5y)+3y = 11
32-10y+3y = 11
-7y = 11-32
-7y = -21(-1)
y = 21/7 = 3*