设\(\overrightarrow{a}=(x,1)\),\(\overrightarrow{b}=(2,-1)\),\(\overrightarrow{c}=(x-m,m-1)(x\in R,m\in R).\)
\((1)\)若\(\overrightarrow{a}\)与\(\overrightarrow{b}\)的夹角为钝角,求\(x\)的取值范围\(;\)
\((2)\)解关于\(x\)的不等式\(\left| \overrightarrow{a}+\overrightarrow{c} \right| < \left| \overrightarrow{a}-\overrightarrow{c} \right|\).