Решите системы уравнений методом подстановки: 1.
{ 2x - y = 3
{ 3x + y = -4

2.
{ x - 7y = 23
{ 3x - y = 14

1. x = -0.2; y = -3.4

2. x = 3.75; y = -2.75

Объяснение:

1. 2x - y = 3, y = 2x - 3

  3x + y = 3x + 2x - 3 = 5x - 3 = -4, 5x = -1, x = -0.2, y = 2 * -0.2 - 3 = -3.4

2. x - 7y = 23, x = 23 + 7y

   3x - y = 3(23+7y) - y = 69+21y - y = 69 + 20y = 14, 20y = -55, y = -2.75, x=23+7*-2.75=3.75