a=√3+√2 b=√3-√2 则
a+b=2√3 ,a-b=2√2
ab=(√3+√2)(√3-√2)=3-2=1
则 a^2-ab+b^2=a^2-2ab+b^2+ab=(a-b)^2+ab=(2√2)^2+1=8+1=9
a^2-b^2=(a+b)(a-b)=2√3×2√2＝4√6