（1）原式=（x2-2xy+y2+x2-y2）÷2x=（2x2-2xy）÷2x=x-y；将x=3，y=1.5代入x-y，得：原式=x-y=3-1.5=1.5．（2）B= x?1 (x+1)(x?1) - x+1 (x+1)(x?1) = x?1?x?1 x2?1 =- 2 x2?1 ；故A、B互为相反数，②的结论正确．
