Question

Cho A =3+3^2+3^3+.....+3^9+3^10. Chứng mnh Achia het cho 4

Answer 1

A=(3+3^2)+(3^3+3^4)+....+(3^9+3^10)

  = 3.(1+3)+3^3.(1+3)+...+3^9.(1+3)

  = 3.4+3^3.4+....+3^9.4

  = 4.(3+3^3+....+3^9) chia hết cho 4

=> ĐPCM

k mk nha

Answer 2

\(A=3+3^2+3^3+...+3^9+3^{10}\)10

\(=\left(3+3^2\right)+\left(3^3+3^4\right)+...+\left(3^9+3^{10}\right)\)

\(=3\left(1+3\right)+3^3\left(1+3\right)+...+3^9\left(1+3\right)\)

\(=4\left(3+3^3+...+3^9\right)\) \(⋮4\)