9.
已知数列\(\{a_{n}\}{中},a_{1}= \dfrac {1}{2},{点}(n,2a_{n+1}-a_{n})(n∈N^{*}){在直线}y=x{上}\),
\((\)Ⅰ\()\)计算\(a_{2}\),\(a_{3}\),\(a_{4}\)的值;
\((\)Ⅱ\()\)令\(b_{n}=a_{n+1}-a_{n}-1\),求证:数列\(\{b_{n}\}\)是等比数列;
\((\)Ⅲ\()\)设\(S_{n}\)、\(T_{n}\)分别为数列\(\{a_{n}\}\)、\(\{b_{n}\}\)的前\(n\)项和,是否存在实数\(λ\),使得数列\(\{ \dfrac {S_{n}+λT_{n}}{n}\}\)为等差数列?若存在,试求出\(λ\)的值;若不存在,请说明理由.