2.
选修\(4-5\):不等式选讲
已知函数\(f\left(x\right)=\left|3x+2\right| \).
\((1)\)解不等式\(f\left(x\right) < 4-\left|x-1\right| \);
\((2)\)已知\(m+n=1(m,n > 0)\),若\(\left|x-a\right|- \dfrac{1}{3}f\left(x\right)\leqslant \dfrac{1}{m}+ \dfrac{1}{n}\left(a > 0\right) \)恒成立,求实数\(a\)的取值范围.