3.
\((\)活页\(89\)页第\(10\)题\()\)已知数列\(\{a_{n}\}\)满足\(a_{n+1}= \dfrac{1}{2}a_{n}+ \dfrac{1}{3}(n=1,2,3,…)\).
\((1)\)当\(a_{n}\neq \dfrac{2}{3}\)时,求证\(\left\{ \left. a_{n}- \dfrac{2}{3} \right. \right\}\)是等比数列;
\((2)\)当\(a_{1}= \dfrac{7}{6}\)时,求数列\(\{a_{n}\}\)的通项公式.