3.
已知函数\(f(x)= \begin{cases} \overset{-x(x+2)^{2},-3\leqslant x\leqslant 0}{2e^{x}(4-x)-8,x > 0}\end{cases}\)如果使等式\( \dfrac {f(x_{1})}{x_{1}+4}= \dfrac {f(x_{2})}{x_{2}+2}= \dfrac {2f(x_{3})}{2x_{3}+1}\)成立的实数\(x_{1}\),\(x_{3}\)分别都有\(3\)个,而使该等式成立的实数\(x_{2}\)仅有\(2\)个,则\( \dfrac {f(x_{2})}{x_{2}+2}\)的取值范围是 ______ .