Question

Tim x:
1/3+1/6+1/10+...+2/x(x+1)=2015/2017

 

Answer 1

\(\frac{2}{6}+\frac{2}{12}+...+\frac{2}{x\left(x+1\right)}=\frac{2015}{2017}\)

\(2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2015}{2017}\)

\(2\left(\frac{1}{2}-\frac{1}{x+1}\right)=\frac{2015}{2017}\)

\(\frac{1}{2}-\frac{1}{x+1}=\frac{2015}{2017}:2\)

\(\frac{1}{x+1}=\frac{1}{2}-\frac{2015}{4034}\)

\(\frac{1}{x+1}=\frac{1}{2017}\)

=>x+1=2017

=>x=2016

Answer 2

\(\frac{2}{6}+\frac{2}{12}+...+\frac{2}{x\left(x+1\right)}=\frac{2015}{2016}\)

\(2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2015}{2016}\)

\(2\left(\frac{1}{2}-\frac{1}{x+1}\right)=\frac{2015}{2016}\)

\(\frac{1}{2}-\frac{1}{x+1}=\frac{2015}{2016}:2\)

\(\frac{1}{x+1}=\frac{1}{2}-\frac{2015}{4032}\)

\(\frac{1}{x+1}=\frac{1}{4032}\)

=>x+1=4032

=>x=4031

Answer 3

Gap lam roi....

Answer 4

Hinh nhu ban sai de roi

Answer 5

ko sai đâu đúng 100%

Answer 6

quy đồng nó nên sao cho khi rút gọn phân số giữ nguyên giá trị là đc

Answer 7

Nhung kia la 2015/2017 ma....

Answer 8

x=4031

Answer 9

lộn 2016