[(x+1)分之1-1]÷(x²-1)分之x
=[(x+1)分之1-(x+1)分之(x+1)]÷(x²-1)分之x
=(x+1)分之[1-(x+1)]÷[(x+1)(x-1)]分之x
=-(x+1)分之x×x分之[(x+1)(x-1)]
=-(x-1)
=1-x