6.
若函数\(f\)\((\)\(x\)\()\)具有性质:\(f\left( \dfrac{1}{x}\right)=-f\left(x\right) \),则称\(f\)\((\)\(x\)\()\)是满足“倒负”变换的函数.
下列四个函数:
\(①\)
\(f\)\(( \)
\(x\)\()=\)
\(\log _{a}x\)\(( \)
\(a\)\( > 0\)且
\(a\)\(\neq 1)\);
\(②\)
\(f\)\(( \)
\(x\)\()=\)
\(a^{x}\)\(( \)
\(a\)\( > 0\)且
\(a\)\(\neq 1)\);
\(③y=x- \dfrac{1}{x} \);
\(④f\left(x\right)=\begin{cases}x,(0 < x < 1) \\ 0,(x=1) \\ - \dfrac{1}{x},(x > 1)\end{cases} \).
其中,满足“倒负”变换的所有函数的序号是______.