Question

[Yêu Hay Ko Yêu]

Tìm STN n để :

2n + 7 chia hết cho 2n + 1

Tìm STN m để :

3m - 9 chia hết cho 3m - 1

Answer 1

[Hoàng Thanh Huyền]

a) \(2n+7⋮2n+1\)

\(\Rightarrow\left(2n+1\right)+6⋮2n+1\)

\(\Rightarrow6⋮2n+1\)(vì \(2n+1⋮2n+1\))

\(\Rightarrow2n+1\inƯ\left(6\right)\)

\(\Rightarrow2n+1\in\left\{1;2;3;6\right\}\)

\(\Rightarrow\)\(2n\in\left\{0;1;2;5\right\}\)

\(\Rightarrow n\in\left\{0;1\right\}\)

b) \(3m-9⋮3m-1\)

\(\Rightarrow\left(3m-1\right)-8⋮3m-1\)

\(\Rightarrow8⋮3m-1\)(vì \(3m-1⋮3m-1\))

\(\Rightarrow3m-1\inƯ\left(8\right)\)

\(\Rightarrow3m-1\in\left\{1;2;4;8\right\}\)

\(\Rightarrow3m\in\left\{2;3;5;9\right\}\)

\(\Rightarrow m\in\left\{1;3\right\}\)

Hok "tuốt" nha^^