@py
Bài làm :
`A = ( 7n + 1 ) . ( 8^8 + 2^20 )`
`A =( 7n + 1 ) . [(2^3)^8 + 2^20]`
`A = ( 7n + 1 ) . ( 2^3 . 8 + 2^20 )`
`A = ( 7n + 1 ) . ( 2^20 . 2^4 + 2^20 )`
`A = ( 7n + 1 ) . [ 2^20 . (16 + 1)]`
`A = ( 7n + 1 ) . ( 2^20 . 17 ) ⋮ 17`
Vậy `A ⋮ 17`