\[\left( \frac{x^{2} + 4x}{x + 2} \right)^{2} - \frac{x^{2} + 4x}{x + 2} - 6 \leq 0\]
\[t = \frac{x^{2} + 4x}{x + 2}\]
\[t^{2} - t - 6 \leq 0\]
\[(t - 3)(t + 2) \leq 0\]
\[- 2 \leq t \leq 3 \Longrightarrow\]
\[\Longrightarrow - 2 \leq \frac{x^{2} + 4x}{x + 2} \leq 3\]
\[\left\{ \begin{matrix} \frac{x^{2} + 4x}{x + 2} \geq - 2 \\ \frac{x^{2} + 4x}{x + 2} \leq 3\ \ \ \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} \frac{x^{2} + 4x + 2 \cdot (x + 2)}{x + 2} \geq 0 \\ \frac{x^{2} + 4x - 3 \cdot (x + 2)}{x + 2} \leq 0 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} \frac{x^{2} + 4x + 2x + 4}{x + 2} \geq 0 \\ \frac{x^{2} + 4x - 3x - 6}{x + 2} \leq 0 \\ \end{matrix} \right.\ \]
\[\left\{ \begin{matrix} \frac{x^{2} + 6x + 4}{x + 2} \geq 0 \\ \frac{x^{2} + x - 6}{x + 2} \leq 0\ \ \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} \frac{\left( x + 3 - \sqrt{5} \right)\left( x + 3 + \sqrt{5} \right)}{x + 2} \geq 0 \\ \frac{(x - 2)(x + 3)}{x + 2} \leq 0\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \]