a-b=2√3-1
两边平方
(a-b)²=12-4√3+1
a²-2ab+b²=13-4√3
a²+b²=13-4√3+2ab=13-2√3
(a+b)²
=a²+2ab+b
=13
a+b=±√13
所以原式=±√13(2√3-1)
=2√39-√13或-2√39+√13