1/(x2-5x+6) - 1/(4x-x2-3) - 1/(3x-x2-2)
=1/(x2-5x+6) + 1/(x2-4x+3) + 1/(x2-3x+2)
=1/(x-2)(x-3)+1/(x-3)(x-1)+1/(x-2)(x-1)
=1/(x-3)-1/(x-2)+1/2(x-3)-1/2(x-1)+1/(x-2)-1/(x-1)
=3/2(x-3)-3/2(x-1)=3/(x-3)(x-1)