Question

[Hà Ngọc Linh]

Tìm STN n, sao cho:

a,5n+7 chia hết cho n

b,n+9 chia hết cho n+4

c,2n+1 chia hết cho n-3

Answer 1

[ᵃʳᵐʸ•Huyền ︿ Anh⁀²⁰⁰⁶ ❄(Team★BTS)❄]

a) Vì 5n + 7 chia hết cho n

\(\Rightarrow7⋮n\Rightarrow n\inƯ\left(7\right)\Rightarrow n\in\left\{\pm1;\pm7\right\}\)

Vậy \(n\in\left\{\pm1;\pm7\right\}\)

Answer 2

[ᵃʳᵐʸ•Huyền ︿ Anh⁀²⁰⁰⁶ ❄(Team★BTS)❄]

b) Vì n + 9 chia hết cho n +4

\(\Rightarrow\left(n+4\right)+5⋮n+4\)

\(\Rightarrow5⋮n+4\)

\(\Rightarrow n+4\inƯ\left(5\right)\)

\(\Rightarrow n+4\in\left\{\pm1;\pm5\right\}\)

\(\Rightarrow n\in\left\{-3;-5;-1;-9\right\}\) \(\inℕ\)

Vậy \(n\in\left\{-3;-5;-1;-9\right\}\)