Решите уравнение) № 378 1) 5y + (8y+9) = 100 2) x - (50-x) = 12 3) (18-3x) - (4+2x) = -6 4) x + (x+1) + (x+2) = 9 5) (z-2) + (z-1) + z=-3 6) 21 + (20-4x) - (11-2x) = 0 № 379 1) 4 (x-7) = 3x+5 2) - 5x+3 (3+2x) = 7 3) 30-x=3 (20-x) 4) 2u-3 (7-2u) = 3 5) 12-y=5 (4-2y) + 10 6) 2-2 (x-8) = 4x-4.

Решаем простые уравнения с одним неизвестным:

1) 5y + (8y + 9) = 100;

5y + 8y + 9 = 100;

13y = 100 - 9;

y = 91 / 13;

y = 7;

2) x - (50 - x) = 12;

2x = 50 + 12;

x = 62 / 2;

x = 31;

x - 50 + x = 12;

3) (18 - 3x) - (4 + 2x) = - 6;

18 - 3x - 4 - 2x = - 6;

14 - 5x = - 6;

5x = 14 + 6;

x = 20 / 5;

x = 4;

4) x + (x + 1) + (x + 2) = 9;

x + x + 1 + x + 2 = 9;

3x + 3 = 9;

3x = 9 - 3;

x = 6 / 3;

x = 2;

5) (z - 2) + (z - 1) + z = - 3;

z - 2 + z - 1 + z = - 3;

3z - 3 = - 3;

z - 1 = - 1;

z = - 1 + 1;

z = 0;

6) 21 + (20 - 4x) - (11 - 2x) = 0;

21 + 20 - 4x - 11 + 2x = 0;

31 - 2x = 0;

- 2x = - 31;

x = 31 / 2;

x = 15,5;

7) 4 (x - 7) = 3x + 5;

4x - 28 = 3x + 5;

4x - 3x = 28 + 5;

x = 33;

8) - 5x + 3 (3 + 2x) = 7;

- 5x + 9 + 6x = 7;

x = 7 - 9;

x = - 2;

9) 30 - x = 3 (20 - x);

30 - x = 60 - 3x;

3 х - x = 60 - 30;

2 х = 30;

х = 30 / 2;

х = 15;

10) 2u - 3 (7 - 2u) = 3;

2u - 21 + 6u = 3;

8u = 3 + 21;

u = 24 / 8;

u = 3;

11) 12 - y = 5 (4 - 2y) + 10;

12 - y = 20 - 10y + 10;

10y - y = 20 - 12 + 10;

9y = 18;

y = 18 / 9;

y = 2;

12) 2 - 2 (x - 8) = 4x - 4;

2 - 2x + 16 = 4x - 4;

- 2x + 18 = 4x - 4;

2x + 4x = 18 + 4;

x = 22 / 6;

x = 3,67.