A=3/1*3+3/3*5+3/5*7+...+3/2015*2017

A=3/2*(2/1*3+2/3*5+2/5*7+...+2/2015*2017)

A=3/2*(1-1/3+1/3-1/5+1/5-1/7+...+1/2015-1/2017)

A=3/2*(1-1/2017)

A=3/2*2016/2017

A=3024/2017

A= \(\frac{3}{1.3}\)+\(\frac{3}{3.5}\)+\(\frac{3}{5.7}\)+....+\(\frac{3}{2015.2017}\)

A= \(\frac{3}{2}\).(\(\frac{2}{1.3}\)+\(\frac{2}{3.5}\)+\(\frac{2}{5.7}\)+...+\(\frac{2}{2015.2017}\))

A= \(\frac{3}{2}\).( 1- \(\frac{1}{3}\)+ \(\frac{1}{3}\)- \(\frac{1}{5}\)+\(\frac{1}{5}\)-\(\frac{1}{7}\)+... \(\frac{1}{2015}\)- \(\frac{1}{2017}\))

A= \(\frac{3}{2}\).(1- \(\frac{1}{2017}\))

A= \(\frac{3}{2}\). \(\frac{2016}{2017}\)

A= \(\frac{3024}{2017}\)

A=4/3+9/8+16/15+..............+4064256/4064255

A=1+1/3+1+1/8+1/15+...............+1/4064255

A=(1+1+...+1)+(1/3+1/8+...+1/406255)          (có 2015 số 1)

A=2015+(1/1.3+1/2.4+...........+1/2015.2017)
A=2015+1/2(1/1-1/3+1/2-1/4+1/3-1/5+1/4-1/6+1/5-1/7+....+1/2012-1/2014+1/2013-1/2015+1/2014-1/2016+1/2015-1/2017)

A=2015+1/2(1+1/2-1/2016-1/2017)

A=2015,749504

                                k cho mình nhé mình k lại cho

=1-1/3+1/3-1/5+...+1/2015-1/2017

=1-1/2017

=2016/2017

http://olm.vn/hoi-dap/question/161872.html

B=1/1.3+1/3.5+...+1/2015.2017

B= 1/2 . 2. ( 1/1.3+1/3.5 + .... + 1/2015 .2017)

B = 1/2 . ( 2/1.3 + 2/3.5 + ......+ 2/2015.2017)

B = 1/2. ( 1/1+ -1/3 + 1/3 + -1/5 + 1/5 +....+ 1/2015 + -1/2017)

B= 1/2 . ( 1/1 + -1 / 2017) = 1/2 . 2016 / 2017 = 2016 / 4034

Vậy B = 2016 / 4034 nha bn.pham hong thai

Dễ thôi:

Khoảng cách là 2

\(\frac{1}{2}.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{2015}-\frac{1}{2017}\right)\)

\(\frac{1}{2}.\left(1-\frac{1}{2017}\right)=\frac{1}{2}.\frac{2016}{2017}=\frac{1008}{2017}\)

cảm ơn bạn đã giúp mình!!

\(\dfrac{4}{1.3}+\dfrac{4}{3.5}+...........+\dfrac{4}{2015.2017}\)

\(=2\left(\dfrac{2}{1.3}+\dfrac{2}{3.5}+............+\dfrac{2}{2015.2017}\right)\)

\(=2\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+.........+\dfrac{1}{2015}-\dfrac{1}{2017}\right)\)

\(=2\left(1-\dfrac{1}{2017}\right)\)

\(=2.\dfrac{2016}{2017}=\dfrac{4032}{2017}\)

\(\dfrac{4}{1.3}+\dfrac{4}{3.5}+...+\dfrac{4}{2015.2017}\)

= 2.(\(\dfrac{2}{1.3}+\dfrac{1}{3.5}+...+\dfrac{2}{2015.2017}\))

= 2.(1 - \(\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+...+\dfrac{1}{2015}-\dfrac{1}{2017}\))

= 2.(1 - \(\dfrac{1}{2017}\))

= 2.\(\dfrac{2016}{2017}\)

= \(\dfrac{4032}{2017}\)

@Nguyễn Thị Ngọc Anh

\(\frac{2016}{1.3}+\frac{2016}{3.5}+\frac{2016}{5.7}+....+\frac{2016}{2015.2017}\)

\(=1008.\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{2015.2017}\right)\)

\(=1008.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{2015}-\frac{1}{2017}\right)\)

\(=1008.\left(1-\frac{1}{2017}\right)\)

\(=1008.\frac{2016}{2017}\)

147852.