Question

cho A = 2+2 mũ 2 + 2 mũ 3 +...+2 mũ 60.

chứng tỏ rằng  A  chia hết cho 3;7;5 . ai bít lm k giúp mik mik hok dốt lắm :) cảm ơn mn

 

Answer 1

\(A=2\left(1+2\right)+2^3\left(1+2\right)+...+2^{59}\left(1+2\right)\)

\(=3\left(2+2^3+...+2^{59}\right)⋮3\)

\(A=2\left(1+2+2^2\right)+...+2^{58}\left(1+2+2^2\right)\)

\(=7\left(2+...+2^{58}\right)⋮7\)