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.