6.
\((1)\)幂函数\(f(x)\)的图象过点\((4, \dfrac{1}{2}) .\)那么\(f(8)\)的值为________.
\((2)\)已知集合\(A\)中元素\((x,y)\)在映射\(f\)下对应\(B\)中元素\((x+y,x-y)\),则\(B\)中元素\((4,-2)\)在\(A\)中对应的元素为________.
\((3)\)函数\(f(x)={{\log }_{\frac{{1}}{3}}}({{x}^{{2}}}-2x-3)\)的单调减区间为________.
\((4)\)已知函数\(f(x)\)满足对任意实数\(m\),\(n\),都有\(f(m+n)=f(m)+f(n)-1\),设\(g(x)=f(x)+ \dfrac{{a}^{x}}{{a}^{x}+1}(a > 0,a\neq 1) \),若\(g(\ln 2017)=2018\),则\(g\left( \ln \dfrac{1}{2017} \right)=\)________.