3.
Ⅰ\(.\)在直角坐标系\(xOy\)中,直线\({{l}_{1}}\)的参数方程为\(\begin{cases} & x=2{+}t, \\ & y=kt, \end{cases}\)\((t\)为参数\()\),直线\({{l}_{2}}\)的参数方程为\(\begin{cases}x=-2+m \\ y= \dfrac{m}{k}\end{cases} (m\)为参数\()\)\(.\)设\(l\)\({\,\!}_{1}\)与\(l\)\({\,\!}_{2}\)的交点为\(P\),当\(k\)变化时,\(P\)的轨迹为曲线\(C\).
\((1)\)写出\(C\)的普通方程;
\((2)\)以坐标原点为极点,\(x\)轴正半轴为极轴建立极坐标系,设\(l_{3}\):\(ρ(\cos θ+\sin θ)−\sqrt{2}=0\),\(M\)为\(l_{3}\)与\(C\)的交点,求\(M\)的极径.
Ⅱ\(.\)已知函数\(f(x)\)\(=│x+1│–│x–2│\).
\((1)\)求不等式\(f(x)\geqslant 1\)的解集;
\((2)\)若不等式\(f(x)\geqslant x^{2}–x +m\)的解集非空,求实数\(m\)的取值范围.