Реши уравнения 20-25.

20. $x^2 = -4x + 32$ $x^2 + 4x - 32 = 0$ $D = 4^2 - 4*(-32) = 16 + 128 = 144$ $x_1 = (-4 + \sqrt{144}) / 2 = (-4 + 12) / 2 = 8 / 2 = 4$ $x_2 = (-4 - \sqrt{144}) / 2 = (-4 - 12) / 2 = -16 / 2 = -8$ **Ответ: x₁=4, x₂=-8** 21. $10x^2 - 17x + 34 = 7x^2 - 26x + 28$ $3x^2 + 9x + 6 = 0$ $x^2 + 3x + 2 = 0$ $D = 3^2 - 4*2 = 9 - 8 = 1$ $x_1 = (-3 + \sqrt{1}) / 2 = (-3 + 1) / 2 = -2 / 2 = -1$ $x_2 = (-3 - \sqrt{1}) / 2 = (-3 - 1) / 2 = -4 / 2 = -2$ **Ответ: -2;-1** 22. $-3x^2 + 5x - 3 = -x^2 + 3x + (2 - 2x^2)$ $-3x^2 + 5x - 3 = -3x^2 + 3x + 2$ $2x = 5$ $x = 2.5$ **Ответ: 2,5** 23. $-3x^2 + x + 9 = -x^2 - 4x + (-2 - 2x^2)$ $-3x^2 + x + 9 = -3x^2 - 4x - 2$ $5x = -11$ $x = -2.2$ **Ответ: -2,2** 24. $-3x^2 + 4x - 7 = -x^2 + 5x - (-1 + 2x^2)$ $-3x^2 + 4x - 7 = -3x^2 + 5x + 1$ $-x = 8$ $x = -8$ **Ответ: -8** 25. $-3x^2 + 2x + 6 = -x^2 + 3x - (-3 + 2x^2)$ $-3x^2 + 2x + 6 = -3x^2 + 3x + 3$ $-x = -3$ $x = 3$ **Ответ: 3**