Question

tính tổng:

Q= 1/3.5 + 1/5.7+ 1/9.7+...........+1/2013.2015.

 

Answer 1

Q= 1/3.5 + 1/5.7+ 1/9.7+...........+1/2013.2015.

Q = 1/2 . 2 . ﴾ 1/3.5+1/5.7+1/7.9+1/9.11 +........+1/2013.2015﴿

Q = 1/2 . ﴾2/3.5 + 2/5.7+2/7.9+2/9.11+.......+2/2013.2015﴿

Q = 1/2 . [1/3+ ﴾‐1/5 + 1/5﴿ + ﴾‐1/7+1/7﴿+ ﴾‐1/9 + 1/9﴿+ ‐1/11 +......+1/2013 + ‐ 1/2015]

Q= 1/2 . ﴾ 1/3 + ‐1/2015 ﴿

Q = 1/2 . 2012/6045 = 1006/6045.

=> Q = 1006 / 6045 

k nhé

Answer 2

\(2Q=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2013}-\frac{1}{2015}\)

\(2Q=\frac{1}{3}-\frac{1}{2015}\)

\(2Q=\frac{2012}{6045}\)

\(Q=\frac{1006}{6045}\)

Answer 3

Q= 1/3.5 + 1/5.7+ 1/9.7+...........+1/2013.2015.

Q = 1/2 . 2 . ( 1/3.5+1/5.7+1/7.9+1/9.11 +........+1/2013.2015)

Q = 1/2 . (2/3.5 + 2/5.7+2/7.9+2/9.11+.......+2/2013.2015)

Q = 1/2 . [1/3+ (-1/5 + 1/5) + (-1/7+1/7)+ (-1/9 + 1/9)+ -1/11 +......+1/2013 + - 1/2015]

Q= 1/2 . ( 1/3 + -1/2015 )

Q = 1/2 . 2012/6045 = 1006/6045.

=> Q = 1006 / 6045