5.
\((1)\)已知\(f\)\((\)\(x\)\()=\)\(x\)\({\,\!}^{3}+3\)\(x\)\({\,\!}^{2}+\)\(a\)\((\)\(a\)为常数\()\),在\([-3,3]\)上有最小值\(3\),那么在\([-3,3]\)上\(f\)\((\)\(x\)\()\)的最大值是________________.
\((2)\)如图阴影部分是由曲线\(y\)\(= \dfrac{1}{x}\)、\(y\)\({\,\!}^{2}=\)\(x\)与直线\(x\)\(=2\)、\(y\)\(=0\)围成,则其面积为______.
\((3)\)函数\(f\)\((\)\(x\)\()=\)\(ax\)\({\,\!}^{3}-3\)\(x\)在区间\((-1,1)\)上为单调减函数,则\(a\)的取值范围是__________.
\((4)\)已知函数\(f\)\((\)\(x\)\()\)的图象在\([\)\(a\),\(b\)\(]\)上连续不断,定义:\(f\)\({\,\!}_{1}(\)\(x\)\()=min\{\)\(f\)\((\)\(t\)\()|\)\(a\)\(\leqslant \)\(t\)\(\leqslant \)\(x\)\(\}(\)\(x\)\(∈[\)\(a\),\(b\)\(])\),\(f\)\({\,\!}_{2}(\)\(x\)\()=max\{\)\(f\)\((\)\(t\)\()|\)\(a\)\(\leqslant \)\(t\)\(\leqslant \)\(x\)\(\}(\)\(x\)\(∈[\)\(a\),\(b\)\(])\),其中,\(min\{\)\(f\)\((\)\(x\)\()|\)\(x\)\(∈\)\(D\)\(\}\)表示函数\(f\)\((\)\(x\)\()\)在区间\(D\)上的最小值,\(max\{\)\(f\)\((\)\(x\)\()|\)\(x\)\(∈\)\(D\)\(\}\)表示函数\(f\)\((\)\(x\)\()\)在区间\(D\)上的最大值\(.\)若存在最小正整数\(k\),使得\(f\)\({\,\!}_{2}(\)\(x\)\()-\)\(f\)\({\,\!}_{1}(\)\(x\)\()\leqslant \)\(k\)\((\)\(x\)\(-\)\(a\)\()\)对任意的\(x\)\(∈[\)\(a\),\(b\)\(]\)成立,则称函数为区间\([\)\(a\),\(b\)\(]\)上的“\(k\)阶收缩函数”\(.\)有以下三个命题,其中正确的命题为________________\(.(\)请把正确命题序号填在横线上\()\).
\(①\)若\(f\)\((\)\(x\)\()=\cos \)\(x\),\(x\)\(∈[0,π]\),则\(f\)\({\,\!}_{1}(\)\(x\)\()=\cos \)\(x\),\(x\)\(∈[0,π]\),\(f\)\({\,\!}_{2}(\)\(x\)\()=1\),\(x\)\(∈[0,π]\);
\(②\)函数\(f\)\((\)\(x\)\()=-\)\(x\)\({\,\!}^{3}+3\)\(x\)\({\,\!}^{2}\)是\([0,1]\)上的\(2\)阶收缩函数;
\(③\)若函数\(f\)\((\)\(x\)\()=\)\(x\)\({\,\!}^{2}\),\(x\)\(∈[-1,4]\)是\([-1,4]\)上的“\(k\)阶收缩函数”,则\(k\)\(=4\).