Question

4. Решите систему уравнений способом подстановки: x - 2y = 8,
2х + 5y = 7
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Answer 1

$\left \{ {{x - 2y = 8} \atop {2x + 5y = 7}} \right. \\\left \{ {{x = 8 + 2y} \atop {2(8+2y) + 5y = 7}} \right. \\\left \{ {{x = 8 + 2y} \atop {16 + 4y + 5y = 7}} \right. \\\left \{ {{x = 8 + 2y} \atop {9y = -9}} \right. \\\left \{ {{x = 8 + 2y} \atop {1y = -1}} \right. \\\left \{ {{x = 8 + 2*(-1)} \atop {1y = -1}} \right. \\\left \{ {{x = 6} \atop {1y = -1}} \right.$