Đáp án:
Giải thích các bước giải:
$\begin{array}{l}
\left| {x\left( {x + 5} \right)} \right| = 4x \Leftrightarrow \left\{ \begin{array}{l}
4x \ge 0\\
{x^2}{\left( {x + 5} \right)^2} = 16{x^2}
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
4x \ge 0\\
{x^2}\left[ {{{\left( {x + 5} \right)}^2} - 16} \right] = 0
\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}
x \ge 0\\
\left[ \begin{array}{l}
{x^2} = 0\\
{\left( {x + 5} \right)^2} = 16
\end{array} \right.
\end{array} \right.\\
\Leftrightarrow \left\{ \begin{array}{l}
x \ge 0\\
\left[ \begin{array}{l}
x = 0\\
x + 5 = 4\\
x + 5 = - 4
\end{array} \right.
\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}
x \ge 0\\
\left[ \begin{array}{l}
x = 0\\
x = - 1\\
x = - 9
\end{array} \right.
\end{array} \right. \Leftrightarrow x = 0
\end{array}$
