(a-2)/(a？ - 1)÷(a- 1)-(2a- 1/a+ 1)

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

=(a-2)/(a？ - 1) ÷ (a？ -2a/a+ 1)

=[(a-2)/(a+ 1)(a- 1)]x(a+ 1)/a(a-2)

= 1/(a？ -A.

Is a the equation x? Root of -x =√3

So a? -a=√3

So the original formula = 1/√3=√3/3.