1(10N 1)N N N+ N N+ N+1 1 1 SUY RA ĐPCM

11. - File thứ 1: chuyen-de-so-nguyen-to-hop-so-doi-tuyen-quan_05112020
File thứ 1: chuyen-de-so-nguyen-to-hop-so-doi-tuyen-quan_05112020

11...1211...1 11...10...0 11...1 11...1(10

n

1)

n n n+ n n+ n+1 1 1

suy ra đpcm.

+

−

+

+

n n1 1

(10 1)(10 1)

= = .