(1/x2
分式化简： 1/(x^2-3x+2)+1/(x^2-5x+6)+1/(x^2-4x+3) =1/[(x-1)(x-2)]+1/[(x-2)(x-3)]+1/[(x-3)(x-1)] =[(x-3)+(x-1)+(x-2)]/[(x-1)(x-2)(x-3)] =(3x-6)/[(x-1)(x-2)(x-3)] =3(x-2)/[(x-1)(x-2)(x-3)] =3/[(x-1)(x-3)].