a=(2-√3)/(2+√3),b=(2+√3)/(2-√3) 求（a+b)²;
解;a=(2-√3)/(2+√3)=(2-√3)²/(2+√3)(2-√3)=(4-4√3+3)/(4-3)=7-4√3
b=(2+√3)/(2-√3)=(2+√3)²/(2-√3)(2+√3)=(4+4√3+3)/(4-3)=7+4√3
故(a+b)²=(7-4√3+7+4√3)²=14²=196