Question

Tìm x,x\(\varepsilon\)N

a)12\(⋮\)x+1

b)x+5\(⋮\)x+1

Answer 1

Lời giải:

a) \(12\vdots x+1\Rightarrow x+1\in \text{Ư}(12)\)

Mà \(x\in\mathbb{N}\Rightarrow x+1\in\mathbb{N}\). Do đó \(x+1\in \left\{1; 2;3;4;6;12\right\}\)

\(\Rightarrow x\in \left\{0; 1;2;3;5;11\right\}\)

b)

\(x+5\vdots x+1\)

\(\Rightarrow (x+1)+4\vdots x+1\)

\(\Rightarrow 4\vdots x+1\Rightarrow x+1\in \text{Ư}(4)\). Mà \(x\in \mathbb{N}\Rightarrow x+1\in \mathbb{N}\)

Do đó: \(x+1\in \left\{1;2;4\right\}\)

\(\Rightarrow x\in \left\{0; 1;3\right\}\)