3m?n3m2?3n2a27、-3÷()× (a>0)
2a22a2m?n
1??1??a?ba?b?2ab?a?8、 ?a? 9、 ????a??a?a?ba?b?22
10、
xy?yxxy?yx?yx?xyyx?xy 11、a?2ab?b?ab?a???? ???a?b?a?abb?ab?b?ab 9