Question

21n+22 chia hết cho 7n+2

Answer 1

21n+22 ⋮ 7n+2 ( n ∈ N )

=>21n+6+16 ⋮ 7n+2

=>16 ⋮ 7n+2 (vì 21n+6 ⋮ 7n+2)

=>7n+2 ∈ ƯC(16)

=>7n+2 ∈ {1,2,4,8,16}

=>n ∈ {2}