Tổng S=1^2.C 2018 1.2^0+2^2.C 2018 2.2^1+3^2.C 2018 3.2^2

Câu hỏi :

Tổng $$\begin{gathered} S=1^2.C_{2018}^1.2^0+2^2.C_{2018}^2.2^1 \\ +3^2.C_{2018}^3.2^2+...+{2018}^2.C_{2018}^{2018}.2^{2017} \\ =2018.3^a.(2b+1) \end{gathered}$$,