cach thu nhat :goi so do la : ab => them chu so 0 thi se la ab0
=> ab0 -ab=648
vay suy ra a=7; b=2
cach thu 2 neu them chu so 0 vao tan cung benh phai thi so do se gap 10 lan
tru di 1 lan so do se con 9 phan lay 648 : 9=72
[trpng truong hop neu chia khong het thi chi lay so nguyen ]