[(a^2-b^2)/(a^2b+ab^2)]÷【1-[(a^2+b^2)/(2ab)]】
=(a+b)(a-b)/ab(a+b) × 2ab/[-(a-b)²]
=-2/(a-b)
=-2/(2-√3-2-√3)
=1/√3
=√3/3