de wa
bai dau tien thi ban o tren giai sai roi
bai nay ban phai hoc toan nang cao ve phuong phap dai so va dau hieu chia het cua mot luy thua chu k phai nhu vay.
con bai so 2:
neu co so tia phan biet la n thi so goc se la n(n-1):2=36
den day roi ban tu giai nha
nho thanks mih nha
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
)))