Ответ:

[tex] {x}^{3} + {3x}^{2} - 4x - 12 = 0[/tex]

[tex] {x}^{2} \times (x + 3) - 4(x + 3) = 0[/tex]

[tex](x + 3) \times ( {x}^{2} - 4) = 0[/tex]

[tex]x + 3 =0 \\ {x}^{2} - 4 = 0[/tex]

[tex]x = - 3 \\ x = - 2 \\ x = 2[/tex]

[tex]x_{1} = - 3. x_{2} = - 2. x_{3} = 2 [/tex]