Question

(5n +12 ) chia hết cho (n - 3) tìm số tn n

 

Answer 1

\(\left(5n+12\right)⋮\left(n-3\right)\)

\(\Rightarrow5\left(n-3\right)+27⋮\left(n-3\right)\)

\(\Rightarrow\left(n-3\right)\inƯ\left(27\right)=\left\{1;-1;3;-3;9;-9;27;-27\right\}\)

Do \(n\in N\)

\(\Rightarrow n\in\left\{0;2;4;6;12;30\right\}\)

Answer 2

Ta có: 5n+12 ⋮ n-3

      ⇔ 5(n-3)+27 ⋮ n-3

      ⇔ 27⋮n-3 hay n-3∈Ư_(27​)

mà n là số tự nhiên

⇒ n-3≥-3

hay n-3={-3;-1;1;3;9;27}

  ⇔ n= {0;2;4;6;12;30}

      

Answer 3

Ta có: \(5n+12⋮n-3\)

\(\Leftrightarrow5n-15+27⋮n-3\)

\(\Leftrightarrow n-3\in\left\{1;-1;3;-3;9;-9;27;-27\right\}\)

hay \(n\in\left\{4;2;6;0;12;-6;30;-24\right\}\)