Question

x + 15 chia hết cho x+3

Answer 1

Giải:

\(x+15⋮x+3.\)

\(\Rightarrow\left(x+3\right)+12⋮x+3.\)

mà \(x+3⋮x+3\Rightarrow12⋮x+3\Rightarrow x+3\in U_{\left(12\right)}=\left\{\pm1;\pm2;\pm3;\pm4;\pm6;\pm12\right\}.\)

\(\Rightarrow x=\left\{-4;-2;-1;-5;0;-6;1;-7;3;-9;9;-15\right\}.\)

Vậy.....

Answer 2

x+5 ⋮ x+3

Ta có : x+5= (x+3)+2

Mà x+3 ⋮ x+3

Để x+5 ⋮ x+3 thì 2⋮ x+3

⇒ x+3 ∈ Ư(2)=\(\left\{1;2\right\}\)

Ta có bảng:

x+3	1	2
x	-2	-1

Vậy x ∈ \(\left\{-2;-1\right\}\)