Chung to rang
a) 212 - 27 chia het cho 31
cho abc chia het cho 27
chung to rang bca chia het cho 27
chung to rang 31x+8y chia het cho 27 thi x+2y chia het cho 27 va nguoc lai
A=1+5+5^2+5^3+.....+5^27 chung to rang A chia het cho 6
\(A=\left(1+5\right)+\left(5^2+5^3\right)+.......+\left(5^{26}+5^{27}\right)\)
\(=6+5^2.\left(1+5\right)+..........+5^{26}.\left(1+5\right)\)
\(=6+5^2.6+........+5^{26}.6\)
\(=6.\left(1+5^2+............+5^{26}\right)\) chia hết cho 6
\(\Rightarrowđpcm\)
A = 1 + 5 + 52 + 53 + ... + 527 ( có 28 số, 28 chia hết cho 2)
A = (1 + 5) + (52 + 53) + ... + (526 + 527)
A = 6 + 52.(1 + 5) + ... + 526.(1 + 5)
A = 6 + 52.6 + ... + 526.6
A = 6.(1 + 52 + ... + 526) chia hết cho 6
=> đpcm
Ủng hộ mk nha ♡_♡
Chung to rang : 5^2012+5^2011+5^2010 chia het cho 31
Ta có\(5^{2012}+5^{2011}+5^{2010}=5^{2010}\left(25+5+1\right)=5^{2010}\cdot31⋮31\)(đpcm)
Chung to rang 2+2^2+2^3...+2^2019 chia het cho 31
Ta có :
A=2+2^2+2^3+2^4+...+2^{99}+2^{100}
=> A=\left(2+2^2+2^3+2^4+2^5\right)+....\left(2^{96}+2^{97}+2^{98}+2^{99}+2^{100}\right)
=> A=2\left(1+2+2^2+2^3+2^4\right)+...+2^{96}\left(1+2+2^2+2^3+2^4\right)
=> A=2.31+...+2^{96}.31
=> A=\left(2+...+2^{96}\right)31chia hết cho 31
kick nha
\(Học\) \(tốt\)
Nhầm roài
Chung to rang : A = 10^n +18n - 1 chia het cho 27 ( voi n thuoc so tu nhien)
a chung to rang aaa chia het cho 37
b chung to rang aaaaaa chia het 37
a) Ta co : aaa = a x 111
vì 111 chia hết cho 37 =>a x 111 chia hết cho 37 hay aaa chia hết cho 37
b) Ta có aaaaaa = a x 111111
vi 111111 chia hết cho 37 => a x 111111 chia hết cho 37 hay aaaaaa chia hết cho 37
Dieu phai chung minh
chung to rang :1+ 5+ 52 + ...+ 5404 chia het cho 31
1+5+52+....+5404
= (1+5+52) + (53+54+55) + .......+ (5402 + 5403 + 5404)
= 1(1+5+52) + 53(1+5+52) +......+ 5402(1+5+52)
= 1. 31 + 53. 31 +......+5402. 31
= 31(1 + 53 + ......... + 5402) chia hết cho 31 (đpcm)
1+5+52+....+5404
= (1+5+52) + (53+54+55) + .......+ (5402 + 5403 + 5404)
= 1(1+5+52) + 53(1+5+52) +......+ 5402(1+5+52)
= 1. 31 + 53. 31 +......+5402. 31
= 31(1 + 53 + ......... + 5402) chia hết cho 31 (đpcm)
chung to rang mot so chia cho 27 du 11 voi mot so chia cho 45 du 7 luon chia het cho 9 .
Tổng hay hiệu. Chắc là tổng.
Ta có:
a = 27k + 11 = 45h + 7
27k + 11 + 45h + 7 = 27k + 45k + 18.
Vì 27k, 45h, 18 \(⋮\) 9 nên 27k + 45k + 18 \(⋮\) 9.
\(\Rightarrow\) Điều phải chứng minh