Để 101995 + 8 / 9 là một số tự nhiên <=> 101995 + 8 chia hết cho 9
101995 + 8 = 100....00 ( có 1996 số ) + 8
Vì 1000.....000 + 8 = 1 + 0 + 0 + ... 0 + 8 = 9 chia hết cho 9 nên 101995 + 8 chia hết cho 9
Vậy 101995 + 8 / 9 là 1 số tự nhiên
đề bài sai 8/9 ko phải là số tự nhiên
de ( 10^1995+8 )/9 la so tu nhien thi 10^1995+8 phai chia het cho 9 nen ta co :
10^1995+8 = 1000...000 (1995 so 0)+8
vì số chia hết cho 9 là số có tổng các chữ số bằng 9 nền 1000...000+8 có tổng là 1+0+0+0+...+0+0+8 = 9 nen :
=> 10^1995+8 chia het cho 9
=> 10^1995+8/9 la so tu nhien
Cách 1: 101995 + 8/9 là 1 số tự nhiên \(\Leftrightarrow\) 101995 + 8 \(⋮\) 9
Ta có : 101995 = 1000.....000 ( 1995 chữ số 0) + 8
=99999..99999(1994 chữ số 9) + 1 + 8
=99999...99999(1994 chữ số 9) + 9 \(⋮\)9
\(\Rightarrow\)đpcm
Cách 2:
Ta có 10\(\equiv\)1(mod 9)
\(\Rightarrow\)101995 \(\equiv\)11995 (mod 9) = 1 (mod 10)
8\(\equiv\)8 ( mod 9)
\(\Rightarrow\)101995 + 8 \(\equiv\)9 (mod 9)
\(\Rightarrow\)101995 + 8 \(⋮\)9
\(\Rightarrow\)đpcm.
Đây là cách giải về đồng dư thức
võ nguyễn bảo huy đúng 100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000%
chứng tỏ :(102022+8)chia hết cho 9
