Question

Tìm số nguyên x, biết: ( x + 3).( x – 2) < 0.

Answer 1

\(\left(x+3\right)\left(x-2\right)< 0\\ \Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x+3< 0\\x-2>0\end{matrix}\right.\\\left\{{}\begin{matrix}x+3>0\\x-2< 0\end{matrix}\right.\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x< -3\\x>2\left(vô.lí\right)\end{matrix}\right.\\\left\{{}\begin{matrix}x>-3\\x< 2\end{matrix}\right.\end{matrix}\right.\)

\(\Rightarrow-3< x< 2\\ \Rightarrow x\in\left\{-2;-1;0;1\right\}\)

Answer 2

=>-3<x<2

mà x là số nguyên

nên \(x\in\left\{-2;-1;0;1\right\}\)