已知椭圆\(C\):\( \dfrac {x^{2}}{a^{2}}+ \dfrac {y^{2}}{b^{2}}=1(a > b > 0)\)经过\((1,1)\)与\(( \dfrac { \sqrt {6}}{2}, \dfrac { \sqrt {3}}{2})\)两点.
\((\)Ⅰ\()\)求椭圆\(C\)的方程;
\((\)Ⅱ\()\)过原点的直线\(l\)与椭圆\(C\)交于\(A\)、\(B\)两点,椭圆\(C\)上一点\(M\)满足\(|MA|=|MB|.\)求证:\( \dfrac {1}{|OA|^{2}}+ \dfrac {1}{|OB|^{2}}+ \dfrac {2}{|OM|^{2}}\)为定值.