m = 410 + 411 + ... + 4198 + 4 199 chung minh rang M la boi cua 5
M = (4^10 + 4^11) + .... + (4^198 + 4^199)
M = 4^10.5+....+4^198.5
= 5.(4^10 + 4^12+....+4^198)
Chung minh rang : 5 + 52 + 53 + ... + 58 la boi cua 30
Chung minh rang
a) A=5+5^2+5^3+...+5^8 la boi cua 30
b) B=3+3^2+3^3+...+3^9 la boi cua 273
HELP ME !
chung minh rang
a, tong hai so le lien tiep la boi cua 6
b, tong cua 2 so chan lien tiep khong la boi cua 4
goi a la tap hop boi chung cua a , b
goi b la tap hop uoc chung cua 13 a + 8b va 5 a+3b
chung minh rang a=b
Chung minh rang a thuoc Z thi a (a+2) - a(a-5)-7 la boi cua 7
\(a\left(a+2\right)-a\left(a-5\right)-7=a^2+2a-a^2+5a-7\)
\(=\left(a^2-a^2\right)+\left(2a+5a\right)-7\)
\(=7a-7\)
\(=7\left(a-1\right)⋮7\) (đpcm)
\(a\left(a+2\right)-a\left(a-5\right)-7=a^2+2a-a^2-5a-7\)
\(=\) \(\left(a^2-a^2\right)-\left(2a+5a\right)-7\)
\(=7a-7\)
\(=7\left(a-1\right)\)\(⋮\)\(7\)( đpcm)
\(a\left(a+2\right)-a\left(a-5\right)-7=a^2+2a-a^2-5a-7\)
\(=\) \(\left(a^2-a^2\right)-\left(2a+5a\right)-7\)
\(=7a-7\)
\(=7\left(a-1\right)\)\(⋮\)\(7\)( đpcm)
Chung minh rang a thuoc Z thi a ( a+2) - a ( a-5) -7 la boi cua 7
chung minh rang abcabc la boi cua 77
Ta có: abcabc=abc.1001=abc.13.77 chia hết cho 77
=>abcabc chia hết cho 77
=>abcabc là bội của 77
chung minh rang neu 2 so a,b la 2 so nguyen khac 0 va a la boi cua b;b la boi cua a thi:a=b hoac a=-b
giup mk nhe mk can gap