Question

Resolva o sistema: {10x + 20y= 110}
x + y= 8

Answer 1

x + y= 8   x (-10)

10x + 20y = 110
-10x -10y = - 80
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        +10y = +30
              y = 30/10
              y = 3

x + 3 = 8
x = 8 - 3 
x = 5

S=(5,3)

Answer 2

x + y = 8

10x + 20y = 110

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x + y = 8                 (multiplica-se por -10)

10x + 20y = 110

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-10x - 10y = -80

10x + 20y = 110   

          10y = 30

y = 30/10

y = 3

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x + y = 8

x + 3 = 8

x = 8 - 3

x = 5

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S = {5,3}