Question

Tìm x ϵ Z, bết:
3x +4 ⋮ (x-1)

Answer 1

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

hay \(x\in\left\{2;0;8;-6\right\}\)

Answer 2

\(\dfrac{3x+4}{x-1}=\dfrac{3x-3+3+4}{x-1}=\dfrac{3\left(x-1\right)}{x-1}+\dfrac{7}{x-1}=3+\dfrac{7}{x-1}\)

\(3x+4⋮x-1\Rightarrow x-1\inƯ_{\left(7\right)}=\left\{-7;-1;1;7\right\}\\ \Rightarrow x\in\left\{-6;1;2;8\right\}\)