6.
\((1)\)已知\(a\),\(b\)均为单位向量,它们的夹角为\( \dfrac{π}{3}\),则\(|\)\(a\)\(+\)\(b\)\(|=\)_______.
\((2)\)已知\(\sin \left(\begin{matrix} \begin{matrix}α+ \dfrac{π}{3} \end{matrix}\end{matrix}\right)+\sin α=- \dfrac{4 \sqrt{3}}{5}\),\(- \dfrac{π}{2} < α < 0\),则\(\sin \left(\begin{matrix} \begin{matrix}α+ \dfrac{7π}{6} \end{matrix}\end{matrix}\right)\)等于_______.
\((3)\)已知实数\(x\),\(y\)满足\(\begin{cases} x-3y-6\leqslant 0, \\ y\leqslant 2x+4, \\ 2x+3y-12\leqslant 0, \end{cases}\)直线\((1+λ)x+(1-2λ)y+3λ-12=0(λ∈R)\)过定点\(A(x_{0},y_{0})\),则\(z= \dfrac{y-y_{0}}{x-x_{0}}\)的取值范围为_______.
\((4)\)已知直线\(l\):\(2mx-y-8m-3=0\)和圆\(C\):\(x^{2}+y^{2}-6x+12y+20=0\)相交于\(A\),\(B\)两点,当线段\(AB\)最短时直线\(l\)的方程为_______.