8.
\((1)\)在函数\(y=\dfrac{x-1}{x}\)中,自变量\(x\)的取值范围是___________.
\((2)\)已知\(a\)满足\(\left| 2018-a \right|+\sqrt{a-2019}=a\),则\(a-2018^{2}\)的值是____________.
\((3)\)观察分析下列方程:\(①x+ \dfrac{2}{x}=3 \),\(②x+ \dfrac{6}{x}=5 \),\(③x+ \dfrac{12}{x}=7 \);请利用它们所蕴含的规律,求关于\(x\)的方程\(x+ \dfrac{{n}^{2}+n}{x-3}=2n+4 (n\)为正整数\()\)的根,你的答案是:__________.
\((4)\)如图矩形\(ABCD\)中,\(AD=10\),\(AB=14\),点\(E\)为\(DC\)上一个动点,把\(\triangle ADE\)沿\(AE\)折叠,当点\(D\)的对应点\(D′\)落在\(∠ABC\)的角平分线上时,\(DE\)的长为___________.