设A={1,2,3,4,5,6},定义A上的二元关系: R1={(1,1),(2,2),(3,3),(4,4),(5,5),(6,6)}∪{(1,4),(2,3),(2,6),(3,2),(3,6),(4,1),(6,2),(6,3)}; R2={(1,2),(2,1),(2,2),(3,3),(4,4),(4,5)}. (1)判断R1,R2是否为等价关系.(2)若是等价关系,写...