Помогите с первым пожалуйста

Решите задачу:

$= 7x {}^{2} - x = 0 \\ x(7x - 1) = 0 \\ x = 0 \\ x = \frac{1}{7} \\ (6 - 2x) {}^{2} = 3x - 9 \\ 36 - 24x + 4x {}^{2} = 3x - 9 \\ 4x {}^{2} - 27x + 45 = 0 \\ d = 27 {}^{2} - 16 \times 45 = 9 \\ x1 = \frac{27 + 9}{8} = \frac{36}{8} = \frac{9}{2} \\ x2 = \frac{27 - 9}{8} = \frac{18}{8} = \frac{9}{4} \\ \\ 2 {x}^{3} - 8x {}^{2} + 5x - 20 = 0 \\ 2x {}^{2} (x - 4) + 5(x - 4) \\ (x - 4)(2x {}^{2} + 5) = 0 \\ x1 = 4 \\ 2x {}^{2} + 5 = 0$