Question

Решите уравнение
х3 + 9х2 + 15х – 25 = 0. ​

Answer 1

Ответ:

${x}^{3} + 9 {x}^{2} + 15x - 25 = 0 \\ {x}^{3} - {x}^{2} + 10 {x}^{2} - 10x + 25x - 25 = 0 \\ {x}^{2} (x - 1) + 10x(x - 1) + 25(x - 1) = 0 \\ (x - 1)( {x}^{2} + 10x + 25) = 0 \\ (x - 1) {(x + 5)}^{2} = 0 \\ x - 1 = 0 \\ {(x + 5)}^{2} = 0 \\ x = 1 \\ x = - 5$