bai 1 ;chung minh rang abcd chia het 99 thi ab cong cd chia het 99 va nguoc lai
bai 2;a.8 mu 10 tru 8 mu 9 tru 8 mu 8 chia het 55
b.7mu 6 cong 7 mu 5 tru 7 mu 4 chia het 11
d.10 mu 9 cong10 mu 8 cong 10 mu 7 chia het 555
c.81mu 7 cong 27 mu 9 tru 9 mu 13 chia het 45
3 mu 3 nhan 9 tru 3 mu 4 nhan 3 cong 5 mu 8 nhan 5 mu 0 tru 5 mu 12 chia 25 mu 2
mot phep tru cong cua so bi tru so tru va hieu bang 490 va so chu hon hieu la 129 tim so bi tru va so tr hieu
2 mo ngoac x cong 1 dong ngoac tru 1 bang 3
tổng sau có chia hết cho 2 và 5
A= 2 nhan 3 nhan4 nhan 5 nhan 6 cong 34
B= 2nhan 3 nhan 4 nhan 5 nhan 6 tru 70
C = 4050 cong 1104 nhan 2017
5 mu 6 cia 5 mu 3 cong 3 mu2 nhan 3 mu 3 tru 3 mu 4 nhan 3
tim cac so nguyen x,y,z bt {5x-7} mu 2 cong {6 tru 5y } mu2 cong {5z } mu 2 bang 10
11 nhan 13 nhan 17 cong 165 tru 121
tim n thuoc n biet
f,n cong 15 chia het n tru 4
g,9n cong 23 chia het 3n cong 4
h,48-7n chia het n
k, 5n cong 11 chia het n -1
m,n mu2 cong 8n cong 13 chia het n cong 2