\((1)\)等比数列\(\left\{{a}_{n}\right\} \) 中,\({a}_{1}=-2 \),\({a}_{5}=-8 \),则\({a}_{3}= \)________________.
\((2).\)曲线\(f(x)=x\ln x \)在点\(P(1,0) \)处的切线\(l\)与两坐标轴围成的三角形的面积是__________.
\((3).\)已知实数\(x\),\(y\)满足不等式组\(\begin{cases} x\leqslant 1 \\ x-y+{{m}^{2}}\geqslant 0 \\ x+y-1\geqslant 0 \end{cases}{ }\),若目标函数\(z=-2x+y \)的最大值不超过\(4\),则实数\(m\)的取值范围是.
\((4)\)、已知点\(P\)是双曲线\(\dfrac{{{x}^{2}}}{a}-\dfrac{{{y}^{2}}}{3a}=1(a > 0)\)右支上任意一点,由\(P\)点向两条渐近线引垂线,垂足分别为\(E\)、\(F\),若\(\triangle PEF\)的面积为\(\dfrac{3\sqrt{3}}{8}\),则\({a}\)的值为______.