Question

Resolva os sistemas de equações abaixo;

a {x+y=6
x-y=7

b{x+y=12
x-y=4

c {x+y=25
x+3y=55

d{x+y=4
2x-3y=3 e {x+y=15 2x+y=18

Answer 1

a {x+y=6
    x-y=7
     2x = 13  ==> x = 13/2
      
y = 6 - x ==> y = 6 - 13/2 ==> y = (12-13)/2 ==> y = - 1/2
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b) {x+y=12
      x-y=4
       2x = 16 ==> x = 8

y = 12 - x ==> y = 12 - 8 ==> y = 4
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c {x+y=25(-1)
    x+3y=55

- x- y = - 25
  x + 3y = 55
      2y = 30 ==> y = 15

x = 25 - y ==> x = 25 - 15 ==> x = 10
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d{  x+y=4(-2)
    2x-3y=3

 -2x -2y = - 8
  2x -3y = 3 
      -5y = -5(-1) ==> 5y = 5 ==> y = 1

x = 4 - y ==> x = 4 - 1 ==> x = 3 
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e {x+y=15 (-1)
    2x+y=18

 -x-y= -15 
2x+y=18
   X = 3

y = 15 - x ==> x = 15 - 3 ==> x = 12