Question

resolver esse sistema
2x + 7y = 17
5x - y = -13

Answer 1

2x + 7y = 175x - y = -13      (7)

2x + 7y = 1735x -7y = -91
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37x       =  -74
x = -74 / 37
x = -2

2x + 7y = 17
2 (-2) + 7y = 17
-4 + 7y = 17
7y = 17 + 4
7y = 21
y = 21/7
y = 3

Resposta :
x = -2
y = 3

Answer 2

Método da substituição:

2x + 7y = 17
5x - y = - 13

5x - y = - 13
5x + 13 = y
y = 5x + 13

2x + 7y = 17
2x + 7.(5x + 13) = 17
2x + 35x + 91 = 17
37x = 17 - 91
37x = - 74
x = - 74/37
x = - 2

y = 5x + 13
y = 5. ( - 2)  + 13
y = - 10 + 13
y = 3

R.: x = - 2; y = 3