已知一次函数\(y\)\({\,\!}_{1}\)\(=kx+m\)与二次函数\(y\)\({\,\!}_{2}\)\(=2ax\)\({\,\!}^{2}\)\(+2bx+c(b\)为整数\()\)的图象交于\(A(2-2\)\({\,\!} \sqrt[]{2}\),\(3-2\)\({\,\!} \sqrt[]{2}\)\()\),\(B(2+2\)\({\,\!} \sqrt[]{2}\),\(3+2\)\({\,\!} \sqrt[]{2}\)\()\)两点,二次函数\(y\)\({\,\!}_{2}\)\(=2ax\)\({\,\!}^{2}\)\(+2bx+c\)和二次函数\(y\)\({\,\!}_{3}\)\(=ax\)\({\,\!}^{2}\)\(+bx+c-1\)的最小值的差为\(1\).
\((1)\)求\(y\)\({\,\!}_{1}\),\(y\)\({\,\!}_{2}\),\(y\)\({\,\!}_{3}\)的函数表达式;
\((2)P\)是\(y\)轴上一点,过点\(P\)任意作一射线分别交\(y\)\({\,\!}_{2}\),\(y\)\({\,\!}_{3}\)的图象于\(M\),\(N\),过点\(M\)作直线\(y=-1\)的垂线,垂足为\(G\),过点\(N\)作直线\(y=-3\)的垂线,垂足为\(H.\)是否存在这样的点\(P\),使\(PM=MG\),\(PN=NH\)恒成立,若存在,求出\(P\)点的坐标,并探究\({\,\!} \dfrac{PM}{PN}\)是否为定值;若不存在,请说明理由.