Bài làm:
\(A=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{2017.2019}\)
\(A=\frac{1}{2}\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{2017.2019}\right)\)
\(A=\frac{1}{2}\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2017}-\frac{1}{2019}\right)\)
\(A=\frac{1}{2}\left(1-\frac{1}{2019}\right)\)
\(A=\frac{1}{2}.\frac{2018}{2019}=\frac{1009}{2019}\)
Vậy \(A=\frac{1009}{2019}\)
Học tốt!!!!
\(A=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{2017.2019}\)
\(2A=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2017}-\frac{1}{2019}\)
\(2A=1-\frac{1}{2019}=\frac{2018}{2019}\)
\(A=\frac{2018}{2019}:2=\frac{2018}{2019}.\frac{1}{2}=\frac{2018}{2019.2}\)mt hỏng, tự tính =))
\(A=\frac{1}{1,3}+\frac{1}{1,5}-\frac{1}{5,7}+...+\frac{1}{2017,2019}\)
\(A=\frac{1}{2}\left(\frac{2}{1,3}+\frac{2}{1,5}-\frac{2}{5,7}+...+\frac{2}{2017,2019}\right)\)
\(A=\frac{1}{2}\left(\frac{1}{3}+\frac{1}{3}+\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2017}-\frac{1}{2019}\right)\)
\(A=1-\frac{1}{2019}=\frac{2018}{2019}\)
\(A=\frac{2018}{2019}\times\frac{1}{2}=\frac{2018}{2019}:2=\frac{1009}{2019}\)
\(A=\frac{1009}{2019}\)
https://olm.vn/hoi-dap/detail/259579029594.html bạn help mình được ko ? nếu đc rát mong sự giúp đỡ của bạn :>
*Ryeo*
rjthfhjyhjfjhjhgnhhjnngjn jbngjgigvikghgjhjmhnmjh