$$\frac{6}{(x+1)(x+2)} + \frac{8}{(x-1)(x+4)} = 1$$
$$\frac{6}{x^2 + 3x + 2} + \frac{8}{x^2 + 3x - 4} = 1$$
Пусть $$y = x^2 + 3x$$, тогда:
$$\frac{6}{y + 2} + \frac{8}{y - 4} = 1$$
$$\frac{6(y - 4) + 8(y + 2)}{(y + 2)(y - 4)} = 1$$
$$\frac{6y - 24 + 8y + 16}{y^2 - 4y + 2y - 8} = 1$$
$$\frac{14y - 8}{y^2 - 2y - 8} = 1$$
$$14y - 8 = y^2 - 2y - 8$$
$$y^2 - 16y = 0$$
$$y(y - 16) = 0$$
$$y = 0$$ или $$y = 16$$
1) $$x^2 + 3x = 0$$
$$x(x + 3) = 0$$
$$x = 0$$ или $$x = -3$$
2) $$x^2 + 3x = 16$$
$$x^2 + 3x - 16 = 0$$
$$D = 3^2 - 4 \cdot 1 \cdot (-16) = 9 + 64 = 73$$
$$x_1 = \frac{-3 + \sqrt{73}}{2}$$, $$x_2 = \frac{-3 - \sqrt{73}}{2}$$
Ответ: $$x_1 = 0$$, $$x_2 = -3$$, $$x_3 = \frac{-3 + \sqrt{73}}{2}$$, $$x_4 = \frac{-3 - \sqrt{73}}{2}$$