Question

cho A= 3+3^2+3^3+.....+3^9+3^10. Chứng mink rằng A chia hết cho 4.

Answer 1

A=3+3^2+3^3+....+3^10

=3(1+3)+3^3(1+3)+....+.3^9(1+3)

=4(3+3^3+...+3^9) chia hết cho 4

k cho minh nha

Answer 2

A = 3+3^2+...+ 3^9+3^10

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

=3(3+1)+....= 3^9(3+1)

=3 .4 +....+ 3^9.4

= 4( 3+...+ 3^9) chia hết cho 4