có A và B là số chẵn =>A=2k,B=2q=>A.B=2k.2q=(2.2).(k.q)=4.kq
vậy A.B chia hết cho 4=> A.B chia cho 4 dư 0
(dấu.là dấu nhân)
là 0 đó 1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000%
