\((1)\)若\(1 < a < 8\),\(-4 < b < 2\),则\(a-|b|\)的取值范围是________.
\((2)\)如果关于\(x\)的不等式\(|x-3|+|x-4| < a\)的解集为空集,则实数\(a\)的取值范围为____________.
\((3)\)在直角坐标系\(xoy\)中,以\(O\)为极点,\(x\)轴的正半轴为极轴建立极坐标系\(.\) 已知直线\(l\)的极坐标方程为\(\rho (\sin \theta -3\cos \theta )=0\),曲线\(C\)的方程为\(\begin{cases} x=t-\dfrac{1}{t}, \\ y=t+\dfrac{1}{t} \end{cases}(t\)为参数\()\) ,\(l\)与\(C\)相交于\(A\),\(B\)两点,\(|AB|=\) .
\((4)\)设\(n\)为正整数,\(f(n)=1+ \dfrac{1}{2}+ \dfrac{1}{3}+…+ \dfrac{1}{n}\),计算得\(f(2)= \dfrac{3}{2}\),\(f(4) > 2\),\(f(8) > \dfrac{5}{2}\),\(f(16) > 3\),观察上述结果,可推测一般的结论为____________.