Question

Tìm số nguyên x , biết:

11) ( x - 1) . ( x+3) = 0

12) x ( x + 2) - 3x - 6 = 0

Answer 1

a, Vì : \(\left(x-1\right)\left(x+3\right)=0\)

\(\Rightarrow\left[\begin{matrix}x-1=0\\x+3=0\end{matrix}\right.\) \(\Leftrightarrow\left[\begin{matrix}x=0+1=1\\x=0-3=-3\end{matrix}\right.\)

Vậy x = 1 hoặc x = -3

b, \(x\left(x+2\right)-3x-6=0\Leftrightarrow x\left(x+2\right)-3x=6\)

\(\Leftrightarrow x\left(x+2-3\right)=6\Leftrightarrow x\left(x-1\right)=6\)

\(\Rightarrow x;x-1\in\left\{\pm1;\pm2;\pm3;\pm6\right\}\)

Mà : x và x - 1 là hai số tự nhiên liên tiếp \(\Rightarrow x=3\in Z\)

Answer 2

11) \(\left(x-1\right).\left(x+3\right)=0\)

\(\Rightarrow\left[\begin{matrix}x-1=0\\x+3=0\end{matrix}\right.\Rightarrow\left[\begin{matrix}x=-1\\x=3\end{matrix}\right.\)