$(x + 1)^{4}(2 - x)(3x + 1) \leq 0$
Đặt $f(x) = (x + 1)^{4}(2 - x)(3x + 1)$
+) $f(x) = 0 \Leftrightarrow x = -1; x = 2; x = -\dfrac{1}{3}$
+) Xét dấu $f(x)$
$x$ $-\infty$ $-1$ $-\dfrac{1}{3}$ $2$ $+\infty$
$f(x)$ $+$ $0$ $-$ $0$ $+$ $0$ $-$
$\to f(x) \leq 0 \Leftrightarrow \left[ \begin{array}{l}x \geq 2\\-1 \leq x \leq -\dfrac{1}{3}\end{array} \right.$