a=1/(2+√3)=2-√3
原式
=(a+1)(a-1)/(a-1)-√(a-1)²/[a(a-1)]
=a+1+(a-1)/[a(a-1)]
=a+1+1/a
=2-√3+1+1/(2-√3)
=2-√3+1+2+√3
=5