\(I:\)已知圆\(C\)的极坐标方程为\(\rho =2\cos \theta \),直线\(l\)的参数方程为\(\begin{cases} & x=\dfrac{1}{2}+\dfrac{\sqrt{3}}{2}t \\ & y=\dfrac{1}{2}+\dfrac{1}{2}t \end{cases}\),\((t\)为参数\()\),,点\(A\)的极坐标为\((\dfrac{\sqrt{2}}{2},\dfrac{\pi }{4})\),设直线\(l\)与圆\(C\)交于点\(P\)、\(Q\).
\((1)\)写出圆\(C\)的直角坐标方程;
\((2)\)求\(|AP|·|AQ|\)的值.
\(II.\)设函数\(f(x)=2|x-1|+x-1\),\(g(x)=16x^{2}-8x+1.\)记\(f(x)\leqslant 1\)的解集为\(M\),\(g(x)\leqslant 4\)的解集为\(N\).
\((1)\)求\(M\);
\((2)\)当\(x∈(M∩N) \)时,证明:\({x}^{2}f(x)+x{[f(x)]}^{2}⩽ \dfrac{1}{4} \).