解
(a²+2a+1)/(a²-1)-a/(a-1)
=(a+1)²/(a-1)(a+1)-a/(a-1)
=(a+1)/(a-1)-a/(a-1)
=(a+1-a)/(a-1)
=1/(a-1)
=1/(√3+1-1)
=1/√3
=√3/3