4.
已知函数\(f(x)= \begin{cases} \overset{|x+1|,x\leqslant 0}{|\log _{2}x|,x > 0}\end{cases}\),若方程\(f(x)=a\)有四个不同的解\(x_{1}\),\(x_{2}\),\(x_{3}\),\(x_{4}\),且\(x_{1} < x_{2} < x_{3} < x_{4}\),则\(x_{3}- \dfrac {1}{(x_{1}+x_{2}) x_{ 3 }^{ 2 }x_{4}}\)的取值范围是 ______ .