(a-1/a)/[(a^2-2a+1)/a]
=[(a^2-1)/a]/[(a-1)^2/a]
=(a^2-1)/a*a/(a-1)^2
=(a^2-1)/(a-1)^2
=(a-1)(a+1)/(a-1)^2
=(a+1)/(a-1)