Question

chung to rang: ( abc- cba ) chia het cho 99

Answer 1

Ta có : abc - cba = 100a + 10b + c - 100c -10b - a = ( 100a - a ) + ( 10b - 10b ) - (100c - c )= 99a - 99c = 99. ( a - c ) chia het cho 99

Answer 2

Nguyễn Đăng Mạnh Cường

A=100a+10b+c-(100c+10b+a)= 99a-99c=99(a-c) 
A/99= a-c 
Vậy A chia hết cho 99

Answer 3

Ta có : abc  -cba = 100a + 10b + c -(100c+10b+a)

= 100a  + 10b + c -100c-10b-a

=( 100a-a) - (100c-c)

=99a - 99c = 99(a-c) \(⋮\)99 (đpcm)