解由x/(x-1) -1＝3/(x-1)(x+2)
知两边乘以(x-1)(x+2)
得x（x+2）-(x-1)(x+2) =3
即x^2+2x-（x^2+x-2）=3
即2x^2+x-1=0
即（2x-1）（x+1）=0
解x=1/2或x=-1
检验x=1/2或x=-1是原方程的根.