Ta có: \(B=3+3^2+3^3+.....+3^{101}\)
\(\Rightarrow B=\left(3+3^2+3^3\right)+.....+\left(3^{99}+3^{100}+3^{101}\right)\)
\(\Rightarrow B=3.\left(1+3+3^2\right)+......+3^{99}.\left(1+3+3^2\right)\)
\(\Rightarrow B=13.\left(3+.....+3^{99}\right)⋮13\)
Vậy B chia hết cho 13
Tương tự cho 41