x减二,分之一加,x加一,分之二减,x减一,分之二减,x加二,分之一等于?

1/(x-2) + 2/(x+1) - 2/(x-1) - 1/(x+2)= [1/(x-2) - 1/(x+2)] + [2/(x+1) - 2/(x-1)]= 4/(x^2-4) - 4/(x^2-1)= 4[1/(x^2-4) - 1/(x^2-1)]= 4*3/[(x^2-4)(x^2-1)]= 12/[(x^2-4)(x^2-1)]