МЕТОД ПОДСТАНОВКИ 14.1 Решите систему уравнений:
у
a)
9x + 5,
—6x — 25;
B)
у
-8х - 15,
y = 5х + 24;
у
б)
y = = 13х – 7,
у = 23х – 6;
г)
у = -11х + 9,
у = -21х + 11.​

а) у=9х+5

6х+y=-25

6х+9х+5=-25

15х=-25-5

15х=-30

х=-2

у=9·(-2)+5

у=-18+5

у=-13

в)

y = -8x - 15;

y = 5x + 24,

5x + 24 = -8x - 15;

5x + 8x = -15 - 24;

13x = -39;

x = -39 : 13;

x = -3.

y = 5 * (-3) + 24 = -15 + 24 = 9.

б)

y = 13x - 7;

y = 23x - 6,

23x - 6 = 13x - 7;

y = 13x - 7.

23x - 13x = 6 - 7;

x(23 - 13) = -1;

10x = -1;

x = -1 : 10;

x = -0.1.

y = 13 * (-0.1) - 7 = -1.3 - 7 = -8.3.

ответ: (-0.1; -8.3).

г)

y = -11x + 9;

y = -21x + 11,

-21x + 11 = -11x + 9;

y = -11x + 9.

-21x + 11x = 9 - 11;

-10x = -2;

x = -2 : (-10);

x = 1/5.

x = 1/5 = 0.2;

y = -11 * 1/5 + 9 = -2.2 + 9 = 6.8.

Объяснение: