Question

7+7^2+7^3+7^4+..7^59+7^60 cmr: a chia hết cho 57  mn lm giúp mik vs ạ !!!

Answer 1

= \(\left(7+7^2+7^3\right)+...+\left(7^{58}+7^{59}+7^{60}\right)\)

= \(7\left(1+7+7^2\right)+...+7^{58}\left(1+7+7^2\right)\)

= \(57.7+...+57.7^{58}\) \(⋮57\)

Answer 2

\(=7\left(1+7+7^2\right)+...+7^{58}\left(1+7+7^2\right)\)

\(=57\cdot\left(1+...+7^{58}\right)⋮57\)