分式1/x^2+x-6,1/x^2-9,1/x^2-5x+6的最简公分母是?

1/(x+x-6)=1/[(x-2)(x+3)] 1/(x-9)=1/[(x+3)(x-3)] 1/(x-5x+6)=1/[(x-2)(x-3)] 因此,最简公分母 =(x-2)(x-3)(x+3) =x^3-2x-9x+18