Question

Kết quả phép tính: 1/1.3+1/3.5+1/5.7+...+1/2007.2009+1/2009.2011. Giải thích hộ mình nhé

Answer 1

= 1/2 . (1/1 - 1/3 + 1/3 - 1/5 +... + 1/2009 - 1/2011)

= 1/2 . (1/1 - 1/2011)

= 1/2 . 2010 / 2011

= 1005/2011

Answer 2

= 1 - 1/2011

= 2010 / 2011

Answer 3

   1/2 ( 2/1.3 + 2/3.5 +...+ 2 /2009.2011)

= 1/2 ( 1/1 - 1/3 + 1/3 - 1/5 +... + 1/2009 - 1/2011)

= 1/2( 1/1 - 1/2011)

= 1/2 . 2010 / 2011

=1005/2011