Question

3n +4 chia hết cho n-1

Answer 1

chứng minh 3n+4 chia hết cho n-1 à

Answer 2

3n +4 \(⋮\) n-1

(n+n+n+4)\(⋮\) n-1

[(n-1)+(n-1)+(n-1) +7] \(⋮\) n-1 mà n-1\(⋮\) n-1

=>7 \(⋮\) n-1

=> n-1 \(\in\) Ư(7)

=> n-1 \(\in\) { 1; -1 ;7;-7}

=>n \(\in\) {2;0;8;-6}

Vậy : n \(\in\) {2;0;8;-6}

Answer 3

3n + 4 \(⋮\) n - 1

\(\Leftrightarrow\) 3n - 3 + 7 \(⋮\) n - 1

\(\Leftrightarrow\) 3(n - 1) + 7 \(⋮\) n - 1

\(\Leftrightarrow\) 7 \(⋮\) n - 1

\(\Leftrightarrow\) n - 1 \(\in\) \(\left\{-7;-1;1;7\right\}\)

\(\Leftrightarrow\) n = \(\left\{-6;0;2;8\right\}\)

Vậy n = \(\left\{-6;0;2;8\right\}\)