Đáp án:
$\begin{array}{l}
1)a)5x\left( { - 5x + 1} \right) + 4\left( {x + 3} \right) < - 25{x^2}\\
\Leftrightarrow - 25{x^2} + 5x + 4x + 12 < - 25{x^2}\\
\Leftrightarrow 9x < - 12\\
\Leftrightarrow x < \dfrac{{ - 4}}{3}\\
Vậy\,x < - \dfrac{4}{3}\\
2)\left| {{x^2} + 2x - 1} \right| = 2\\
\Leftrightarrow \left[ \begin{array}{l}
{x^2} + 2x - 1 = 2\\
{x^2} + 2x - 1 = - 2
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
{x^2} + 2x - 3 = 0\\
{x^2} + 2x + 1 = 0
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
\left( {x - 1} \right)\left( {x + 3} \right) = 0\\
{\left( {x + 1} \right)^2} = 0
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = 1\\
x = - 3\\
x = - 1
\end{array} \right.\\
Vậy\,x = 1;x = - 1;x = - 3
\end{array}$
