[(a-1/a )-（a-2/a+1)]/ (2a平方-a/a平方+2a+1)=（a²-1-a²+2a）/(a(a+1))×（a+1）²/a(2a-1)=(2a-1)/(a(a+1))×（a+1）²/[a(2a-1)]=(a+1)/a²因为a²-a-1=0即a²=a+1所以原式=1
