Respostas

2013-11-12T13:09:56-02:00
A) 
x-2y=7
3x+y=35 .(+2)
______
x-2y=7
6x+2y=70
________
7x=77
  x=77/7
  x= 11
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x-2y=7
11-2y=7
2y=7-11
2y=4
 y=4/2
y=2

X=11 ; Y=2
2013-11-12T13:24:22-02:00
A)
x-2y=7      x=7+2y
3x+y=35
3(7+2y)+y=35
21+6y+y=35
21+7y=35
7y=35-21
7y=14
y=14/7
y=2

x=7+2y
x=7+2.2
x=7+4
x=11

b)
x+y=1   x=1-y
x-2y=1
1-y-2y=1
1-3y=1
-3y=1-1  (-1)
3y=-1+1
3y=0

x=1-y
x=1-0
x=1

c)
x+3y=1
5x+3y=17           x=1-3y
5(1-3y)+3y=17
5-15y+3y=17
5-12y=17
-12y=17-5
-12y=12        (-1)
12y=-12
y=-12/12
y=-1

x=1-3y
x=1-3.1
x=1-3
x=-2

d)
x+y=14        x=14-y
2x-y=5
2(14-y)-y=5
28-2y-y=5
28-3y=5
-3y=5-28
-3y=-23  (-1)
3y=23
y=23/3

x=14-23/3
x=42/3--23/3
x=19/3
 







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