Question

Tìm x \(\in\) Z biết ( x + 5 ) . ( 3x - 12 ) > 0

Answer 1

TH1: \(\left\{{}\begin{matrix}x+5>0\\3x-12>0\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}x>-5\\x>4\end{matrix}\right.\)

\(\Rightarrow x=\left\{5;6;7;8;9;...\right\}\)

Kết luận.............

TH2: \(\left\{{}\begin{matrix}x+5< 0\\3x-12< 0\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}x< -5\\x< 4\end{matrix}\right.\)

\(\Rightarrow x=\left\{-6;-7;-8;-9;...\right\}\)

Kết luận.............