已知椭圆\(C\):\( \dfrac {x^{2}}{a^{2}}+ \dfrac {y^{2}}{b^{2}}=1(a > b > 0)\),三点\(P_{1}(1, \dfrac {3}{2})\),\(P_{2}( \dfrac {1}{2},- \dfrac { \sqrt {3}}{2}).P_{3}(-1,- \dfrac {3}{2})\)中恰有二点在椭圆\(C\)上,且离心率为\(e= \dfrac {1}{2}\).
\((1)\)求椭圆\(C\)的方程;
\((2)\)设\(P\)为椭圆\(C\)上任一点,\(A_{1}A_{2}\)为椭圆\(C\)的左右顶点,\(M\)为\(PA_{2}\)中点,求证:直线\(PA_{2}\)与直线\(OM\)它们的斜率之积为定值;
\((3)\)若椭圆\(C\)的右焦点为\(F\),过\(B(4,0)\)的直线\(l\)与椭圆\(C\)交于\(D\),\(E\),求证:直线\(FD\)与直线\(FE\)关于直线\(x=1\)对称.