(x² -9)/(x² -x-6) :(x² -x-12)/(x² -2x-8)=
=(x -3)(x+3)/(x² +2x-3x-6) :(x² +3x-4x-12)/(x² +2x-4x-8)=
=(x -3)(x+3)/[x(x +2)-3(x+2)] :[x(x +3)-4(x+3)]/[x(x +2)-4(x+2)]=
=(x -3)(x+3)/(x +2)(x-3) :(x +3)(x-4)/(x +2)(x-4)=
=(x+3)/(x +2) :(x +3)/(x +2)=
=(x+3)/(x +2) × (x +2)/(x +3)=
=1