Question

[hoàng thăng hậu]

chứng minh rằng A=1+3+3¹+3²+3³+3⁴+.....+3¹⁰²+3¹⁰³chia hết cho 4

Answer 1

[ILoveMath]

\(A=1+3+3^2+3^3+...+3^{102}+3^{103}\)

\(\Rightarrow A=\left(1+3\right)+\left(3^2+3^3\right)+...+\left(3^{102}+3^{103}\right)\)

\(\Rightarrow A=\left(1+3\right)+3^2\left(1+3\right)+...+3^{102}\left(1+3\right)\)

\(\Rightarrow A=\left(1+3\right)\left(1+3^2+...+3^{102}\right)\)

\(\Rightarrow A=4\left(1+3^2+...+3^{102}\right)⋮4\)