a²-a-1=0
所以a+1=a²
原式=(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
=a²/a²
=1