a: \(A=1+2+2^2+...+2^{2023}\)
=>\(2A=2+2^2+2^3+...+2^{2024}\)
=>\(2A-A=2^{2024}+2^{2023}+...+2^2+2-2^{2023}-2^{2022}-...-2^2-2-1\)
=>\(A=2^{2024}-1\)
b: \(A=\left(1+2\right)+2^2+2^3+...+2^{2023}\)
\(=3+2^2\left(1+2\right)+...+2^{2022}\left(1+2\right)\)
\(=3\left(1+2^2+...+2^{2022}\right)⋮3\)