设椭圆\(\dfrac{{{x}^{2}}}{16}+\dfrac{{{y}^{2}}}{12}=1\)上三个点\(M\),\(N\)和\(T\),且\(M\),\(N\)在直线\(x=8\)上的射影分别为\({{M}_{1}},{{N}_{1}}\).
\((1)\)若直线\(MN\)过原点\(O\),直线\(MT\),\(NT\)斜率分别为\({{k}_{1}},{{k}_{2}}\),求证:\({{k}_{1}}\cdot {{k}_{2}}\)为定值;
\((2)\)若\(M\),\(N\)不是椭圆长轴的端点,点\(L\)坐标为\(\left( 3,0 \right)\),\(\Delta {{M}_{1}}{{N}_{1}}L\)与\(\Delta MNL\)面积之比为\(5\),求\(MN\)中点\(K\)的轨迹方程.