8.
.设函数\(f\)\((\)\(x\)\()\)\(=\)\((\)\(x-\)\(1)^{3}\)\(-ax-b\),\(x\)\(∈R\),其中\(a\),\(b\)\(∈R\).
\((1)\)求\(f\)\((\)\(x\)\()\)的单调区间\(;\)
\((2)\)若\(f\)\((\)\(x\)\()\)存在极值点\(x\)\({\,\!}_{0}\),且\(f\)\((\)\(x\)\({\,\!}_{1})\)\(=f\)\((\)\(x\)\({\,\!}_{0})\),其中\(x\)\({\,\!}_{1}\neq \)\(x\)\({\,\!}_{0}\),求证:\(x\)\({\,\!}_{1}\)\(+\)\(2\)\(x\)\({\,\!}_{0}\)\(=\)\(3;\)
\((3)\)设\(a > \)\(0\),函数\(g\)\((\)\(x\)\()\)\(=|f\)\((\)\(x\)\()\)\(|\),求证:\(g\)\((\)\(x\)\()\)在区间\([0,2]\)上的最大值不小于\( \dfrac{1}{4} \).