146. Решите уравнение: 1) 7x² - 28x = 0; 2) 81x³ + 36x² + 4x = 0; 3) x³ - 2x² - 9x + 18 = 0; 4) x⁴ + 4x³ + 4x² + 16 = 0; 5) 8x⁵ - 6x² - 75x + 150 = 0; 6) x⁶ + 4x⁴ + 4x³ - x² - 4x - 4 = 0.

1) $7x^2 - 28x = 0$ $7x(x - 4) = 0$ $x = 0$ или $x = 4$ 2) $81x^3 + 36x^2 + 4x = 0$ $x(81x^2 + 36x + 4) = 0$ $x(9x + 2)^2 = 0$ $x = 0$ или $x = -\frac{2}{9}$ 3) $x^3 - 2x^2 - 9x + 18 = 0$ $x^2(x - 2) - 9(x - 2) = 0$ $(x - 2)(x^2 - 9) = 0$ $(x - 2)(x - 3)(x + 3) = 0$ $x = 2$ или $x = 3$ или $x = -3$ 4) $x^4 + 4x^3 + 4x^2 + 16 = 0$ $x^2(x^2 + 4x + 4) + 16=0$ 5) $8x^5 - 6x^2 - 75x + 150 = 0$ 6) $x^6 + 4x^4 + 4x^3 - x^2 - 4x - 4 = 0$