\(A=2+2^2+2^3+2^4+2^5+2^6+2^7+2^8\)
\(=\left(2+2^2\right)+\left(2^3+2^4\right)+\left(2^5+2^6\right)+\left(2^7+2^8\right)\)
\(=2\left(1+2\right)+2^3\left(1+2\right)+2^5\left(1+2\right)+2^7\left(1+2\right)\)
\(=\left(1+2\right)\left(2+2^3+2^5+2^7\right)\)
\(=3\left(2+2^3+2^5+2^7\right)\)\(⋮\)\(3\)
1.Hay viet vao ben phai so 2005 so co 2 chu so de duoc so nho nhat co 6 chu so khi chia 5 du 1 nhung chia het cho 2
2. Cho A =13 giao thua - 11 giao thua
A co chia het cho 2 hay khong
A co chia ht cho 5 hay khong
3. Tong cac so tu nhien tu 1 den 154
Co chia het cho 2 hay khong
Co chia het cho 5 hay khong
4.
Cho A = 115+118+117+...+11+1
Chung minh rang A chia het cho 5
5.
Chung minh rang voi moi nguoi so tu nhien thi N2+N+6 khong chia het cho 5
6.Trong cac so tu nhien nho hon 1000 co bao nhieu so chia het cho 2 nhung khong chia het cho 5
Tong say co chia het cho 7 khong
B=2+2 mu 2+2 mu 3 +...+2 mu 30
tong day co chia het cho 5 khong \(A=2+2^3+2^4+2^5+2^6+2^7\)
Bai 1.Cho C= 1+7+7^2+7^3+....+7^30.
Chung to C khong chia het cho 57.
Bai 2. Chứng minh ko có số tự nhiên nào chia 15(du 6), con chia 9(du 1).
Bai 3.Chứng minh rằng 3 số tự nhiên liên tiếp thì chia het cho 3 con tong cua 4 so tu nhien lien tiep thi khong chia het cho 4
Bai 4. Chứng minh rang voi "n" la so tu nhien, ta co:
60n+15 chia hết cho 15. Nhung 60n+15 khong chi het cho 30
Các bạn giải giúp mình sẽ tick lien.
a) A=2n+22+23+24+25+26+27+28+29+210
Khong tinh gia tri. Hay chung to A chia het cho 3.
b) Tong sau day co chia het cho 5 khong?
B=40+41+4243+44+45+46+47+48+49+410
khong gia tri xet xem cac tong sau day co chia het cho 9 hay khong 2*3*4*5*6*7+8*9*10*11*12
Cho A = 2 + 2^2+ 2^3 + 2^4 + 2^5 + 2^6 + 2^6 + 2^7 + 2^8 + 2^9. Khong tinh, hay chung to A chia het cho 7.
Ai ma lam nhanh va chinh xac nhat, minh hua se tick cho nha !
a, tong 10^15+8 co chia het cho 2 va 9 khong?
b, tong 10^2010 +8 co chia het cho 9 khong ?
c, 10^2010-4 co chia het cho 3 khong ?
tong sau co chia het cho 3 ko
A= 2+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9+2^10
