8.
已知椭圆\(C\):\( \dfrac {x^{2}}{a^{2}}+ \dfrac {y^{2}}{b^{2}}=1(a > b > 0)\),四点\(P_{1}(1,1)\),\(P_{2}(0,1)\),\(P_{3}(-1, \dfrac { \sqrt {3}}{2})\),\(P_{4}(1, \dfrac { \sqrt {3}}{2})\)中恰有三点在椭圆\(C\)上.
\((1)\)求\(C\)的方程;
\((2)\)设直线\(l\)不经过\(P_{2}\)点且与\(C\)相交于\(A\),\(B\)两点\(.\)若直线\(P_{2}A\)与直线\(P_{2}B\)的斜率的和为\(-1\),证明:\(l\)过定点.