\(A=1+\left(3^1+3^2\right)+\left(3^3+3^4\right)+...+\left(3^{2021}+3^{2022}\right)\)
\(=1+3\left(1+3\right)+3^3\left(1+3\right)+...+3^{2021}\left(1+3\right)\)
\(=1+3.4+3^3.4+...+3^{2021}.4\)
\(=1+4.\left(3+3^3+...+3^{2021}\right)\)
\(\Rightarrow A\) chia 4 dư 1



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