-0,7х (в степени) 3-2,1х (в степени) 2=0 решите уравнение

Решите задачу:

$- 0. {7} {x}^{3} - 2.1 {x}^{2} = 0 \\ - \frac{7}{10} {x}^{3} - \frac{21}{10} {x}^{2} = 0 \\ - {x}^{2} \times ( \frac{7}{10} x - \frac{21}{10} ) = 0 \\ - {x}^{2} \times \frac{7}{10} \times (x + 3) = 0 \\ {x}^{2} \times (x + 3) = 0 \\ {x}^{2} = 0 \\ x + 3 = 0 \\ x = 0 \\ x = - 3\\ x1 = -3 \\ x2 = 0$