[a/(a-1) -2/(a²-1)]÷[1- 1/(a+1)]=[a/(a-1)-2/(a+1)(a-1)]÷[a/(a+1)]=[a(a+1)-2]/(a+1)(a-1)][(a+1)/a]=(a²+a-2)(a+1)/[a(a+1)(a-1)]=(a+2)(a-1)(a+1)/[a(a+1)(a-1)]=(a+2)/a=1+ 2/a