6．
有以下判断：
\(①\)\(f\)\((\)\(x\)\()= \dfrac{|x|}{x}\)与\(g\)\((\)\(x\)\()=\begin{cases} 1\quad \quad x\geqslant 0 \\ -1 x < 0 \end{cases}\)表示同一函数；
\(②\)函数\(y\)\(=\)\(f\)\((\)\(x\)\()\)的图象与直线\(x\)\(=1\)的交点最多有\(1\)个；
\(③\)\(f\)\((\)\(x\)\()=\)\(x\)\({\,\!}^{2}-2\)\(x\)\(+1\)与\(g\)\((\)\(t\)\()=\)\(t\)\({\,\!}^{2}-2\)\(t\)\(+1\)是同一函数；
\(④\)若\(f\)\((\)\(x\)\()=|\)\(x\)\(-1|-|\)\(x\)\(|\)，则\(f\)\(\left(\begin{matrix} \begin{matrix}f\left(\begin{matrix} \begin{matrix} \dfrac{1}{2} \end{matrix}\end{matrix}\right) \end{matrix}\end{matrix}\right)=0\)．
其中正确判断的序号是________．