Đáp án:
$-9<x<2$
Giải thích các bước giải:
$(x +9) (2 -x) > 0$
⇔\(\left[ \begin{array}{l}x+9>0\\2-x>0\end{array} \right.\) hay \(\left[ \begin{array}{l}x+9<0\\2-x<0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x>-9\\-x>-2\end{array} \right.\) hay \(\left[ \begin{array}{l}x<-9\\-x<-2\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x>-9\\x<2\end{array} \right.\) hay \(\left[ \begin{array}{l}x<-9\\x>-2\end{array} \right.\)
⇔$-9<x<2$
