原式=2x/(x²-1)-1/(x-1)-1/(x+1)
=(2x-x-1-x+1)/(x²-1)
=0
2.原式=(x²-1)/(x+2)÷[(-x-1)/(x+2)]
=1-x
把x=1/3代入,得
原式=1-1/3=2/3