Question

Giải bất pt sau : -3 ( x+1 )( x-2 ) > 0

Answer 1

-3(x+1)(x-2)>0

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

=>-1<x<2

Answer 2

\(-3\left(x+1\right)\left(x-2\right)>0\)

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

TH1:

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

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

\(\Leftrightarrow-1< x< 2\)

TH2:

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

\(\left\{{}\begin{matrix}x< -1\\x>2\end{matrix}\right.\)(loại)

Vậy...