6.
\((1)\)设向量\(\overset{\to }{{{a}}}\,\) \(=(-1,3)\),\(\overset{\to }{{{b}}}\,\) \(=(2,\)\(x\)\()\),若\(\overset{\to }{{{a}}}\,\) \(/\!/\)\(\overset{\to }{{{b}}}\,\) ,则\(x\)\(= \)______.
\((2)\)已知\(p\):\(x\)\( < -3\)或\(x\)\( > 1\),\(q\):\(x\)\( > \)\(a\),若\(¬\)\(p\)是\(¬\)\(q\)的充分不必要条件,则\(a\)的取值范围______.
\((3)\)若函数\(f(x)=\dfrac{4x}{x+4}\) 且\({{x}_{1}}=1\) ,\({{x}_{n+1}}=f({{x}_{n}})\) ,则\({{x}_{2017}}\) \(= \)______.
\((4)\)给出下列命题:
\(①\)函数
\(y\)\(=\)
\({\sin }(\dfrac{5\pi }{2}{-}2x)\) 是偶函数;
\(②\)方程
\(x=\dfrac{\pi }{8}\) 是函数
\(y\)\(=\)
\(\sin \)\((2 \)
\(x\)\(+ \dfrac{5π}{4} )\)的图象的一条对称轴方程;
\(③\)若\(α\)、\(β\)是第一象限角,且\(α > β\),则
\(\sin \)\(α > \)
\(\sin \)\(β\);
\(④\)设
\(x\)\({\,\!}_{1}\)、
\(x\)\({\,\!}_{2}\)是关于
\(x\)的方程\(|\)
\(\log _{a}x\)\(|=\)
\(k\)\(( \)
\(a\)\( > 0\),
\(a\)\(\neq 1\),
\(k\)\( > 0)\)的两根,则
\(x\)\({\,\!}_{1}\)
\(x\)\({\,\!}_{2}=1\);
其中正确命题的序号是______\(.(\)填出所有正确命题的序号\()\)