12. 8 ------- - -------=1 X-1. X+1 X+15. 21 -------- - ---------=2 4. X+2 Радцонал

[latex] \frac{12}{x-1} - \frac{8}{x+1} =1|\cdot (x-1)(x+1) \\ 12(x+1)-8(x-1)=(x-1)(x+1) \\ 12x+12-8x+8=x^2-1 \\ x^2-4x-21=0[/latex] По т. ВИета: [latex] \left \{ {{x_1+x_2=4} \atop {x_1\cdot x_2=-21}} \right. \to \left \{ {{x_1=7} \atop {x_2=-3}} \right. [/latex] Ответ: -3 и 7. [latex] \frac{x+15}{4} - \frac{21}{x+2} =2|\cdot 4(x+2) \\ (x+15)(x+2)-21\cdot 4=8(x+2) \\ x^2+17x+30-84=8x+16 \\ x^2+9x-70=0[/latex] По т. Виета: [latex] \left \{ {{x_1+x_2=-9} \atop {x_1\cdot x_2=-70}} \right. \to \left \{ {{x_1=-14} \atop {x_2=5}} \right. [/latex] Ответ: -14 и 5.