1. 15x + 10 = 6x - 8

1. $15x + 10 = 6x - 8$ $15x - 6x = -8 - 10$ $9x = -18$ $x = -2$ 2. $-2(x - 4) = 3 + 7x$ $-2x + 8 = 3 + 7x$ $-2x - 7x = 3 - 8$ $-9x = -5$ $x = 5/9$ 3. $26x - 6 = 8x - 42$ $26x - 8x = -42 + 6$ $18x = -36$ $x = -2$ 4. $10x - 8 = 20x + 74$ $10x - 20x = 74 + 8$ $-10x = 82$ $x = -8,2$ 5. $13x + 8 = 27x + 18$ $13x - 27x = 18 - 8$ $-14x = 10$ $x = -10/14 = -5/7$ 6. $1,2(x - 4) + 4,6 = 0,3(3 + x)$ $1,2x - 4,8 + 4,6 = 0,9 + 0,3x$ $1,2x - 0,2 = 0,9 + 0,3x$ $1,2x - 0,3x = 0,9 + 0,2$ $0,9x = 1,1$ $x = 1,1 / 0,9 = 11/9 = 1\frac{2}{9}$ 7. $-0,6(x - 3) - 3,3 = 0,6(4 - x)$ $-0,6x + 1,8 - 3,3 = 2,4 - 0,6x$ $-0,6x - 1,5 = 2,4 - 0,6x$ $-0,6x + 0,6x = 2,4 + 1,5$ $0 = 3,9$ Уравнение не имеет корней. 8. $\frac{x - 3}{x + 5} = \frac{5}{8}$ $8(x - 3) = 5(x + 5)$ $8x - 24 = 5x + 25$ $3x = 49$ $x = 49/3 = 16\frac{1}{3}$ 9. $\frac{x - 3}{5} = \frac{x + 8}{4}$ $4(x - 3) = 5(x + 8)$ $4x - 12 = 5x + 40$ $-x = 52$ $x = -52$ 10. $\frac{7}{x + 8} = \frac{6}{2 - x}$ $7(2 - x) = 6(x + 8)$ $14 - 7x = 6x + 48$ $-13x = 34$ $x = -34/13 = -2\frac{8}{13}$ 11. $(9y - 2)(2,1 - 7y) = 0$ $9y - 2 = 0 \Rightarrow y = 2/9$ $2,1 - 7y = 0 \Rightarrow 7y = 2,1 \Rightarrow y = 0,3$ Ответ: $y_1 = 2/9, y_2 = 0,3$ 12. $(-2x - 8,4)(0,7x + 4,2) = 0$ $-2x - 8,4 = 0 \Rightarrow -2x = 8,4 \Rightarrow x = -4,2$ $0,7x + 4,2 = 0 \Rightarrow 0,7x = -4,2 \Rightarrow x = -6$ Ответ: $x_1 = -4,2, x_2 = -6$