已知a-b=√3+√2,b-c=√3-√2,求a²+b²+c²-ab-ac-bc的值.将两个已知相加,得：a-c=2√3,有：a²+b²+c²-ab-ac-bc=1/2×[2a²+2b²+2c²-2ab-2ac-2bc]=1/2×[(a²-2ab+b²)+(b&su...