原式=(a+1)/(a-1)-[a/(1/a)]/(a-2a+1)
=(a+1)/(a-1)-a/(a-1)
=[(a+1)(a-1)-a]/(a-1)
=(a-1-a)/(a-1)
=-1/(a-1)
a=-1-√2
原式=-1/(-1-√2-1)=-1/(6+4√2)
=(2√2-3)/2=√2-3/2