解1题：最简公分母是(x+y)x-2y=(x-2y)(x+y)/(x+y)y²/(x+y)与(x-2y)(x+y)/(x+y)有相同的分母解2题：最简公分母是(a-b)(b-c)(a-c)1/[(a-b)(b-c)]=(a-c)/[(a-b)(b-c)(a-c)]1/[(b-c)(c-a)]=-1/[(b-c)(a-c)]= -(a-b)...