Question

Tìm x:

(x-2) (x+2/3) <0

(x+1) (x-2)<0

Answer 1

\(\left(x-2\right)\left(x+\dfrac{2}{3}\right)< 0\)

Với mọi \(x\in R\) thì:

\(x-2< x+\dfrac{2}{3}\) Nên \(\left\{{}\begin{matrix}x-2< 0\\x+\dfrac{2}{3}>0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x< 2\\x>-\dfrac{2}{3}\end{matrix}\right.\)

Suy ra\(-\dfrac{2}{3}< x< 2\)

\(\left(x+1\right)\left(x-2\right)< 0\)

Với mọi \(x\in R\) thì:

\(x-2< x+1\) nên \(\left\{{}\begin{matrix}x-2< 0\\x+1>0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x< 2\\x>-1\end{matrix}\right.\)

Suy ra \(-1< x< 2\)