Question

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

cái đề này là tính nha mấy bạn

 

Answer 1

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

Answer 2

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= \(\frac{3024}{2017}\)