Đáp án:
b) \(\left[ \begin{array}{l}
m > \dfrac{{2 + 2\sqrt 7 }}{3}\\
m < \dfrac{{2 - 2\sqrt 7 }}{3}
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
C2:\\
a)3{x^2} - x - 2 \le 0\\
\to \left( {x - 1} \right)\left( {3x + 2} \right) \le 0\\
\to - \dfrac{2}{3} \le x \le 1\\
b)DK:\left\{ \begin{array}{l}
- 1 < 0\left( {ld} \right)\\
{m^2} + 4m + 4 - 4\left( { - 1} \right)\left( { - {m^2} + 1} \right) < 0
\end{array} \right.\\
\to {m^2} + 4m + 4 - 4{m^2} + 4 < 0\\
\to - 3{m^2} + 4m + 8 < 0\\
\to \left[ \begin{array}{l}
m > \dfrac{{2 + 2\sqrt 7 }}{3}\\
m < \dfrac{{2 - 2\sqrt 7 }}{3}
\end{array} \right.
\end{array}\)
