`Đáp` `án` + `Giải` `thích``các` `bước` `giải`:
`$\frac{1}{1.2}$`+`$\frac{1}{3.4}$`+`$\frac{1}{5.6}$`+...+`$\frac{1}{49.50}$`=`$\frac{1}{26}$`+`$\frac{1}{27}$`+`$\frac{1}{28}$`+...+`$\frac{1}{50}$`
=`1`- `$\frac{1}{2}$`+`$\frac{1}{3}$`-`$\frac{1}{4}$`+`$\frac{1}{5}$`-`$\frac{1}{6}$`+...+`$\frac{1}{49}$`-`$\frac{1}{50}$`
=(`1`+`$\frac{1}{3}$`+`$\frac{1}{5}$`+...+`$\frac{1}{49}$`) - (`$\frac{1}{2}$`+`$\frac{1}{4}$`+`$\frac{1}{6}$`+...`$\frac{1}{50}$`)
=(`1`+`$\frac{1}{3}$`+`$\frac{1}{5}$`+...+`$\frac{1}{50}$`) - `2`(`$\frac{1}{2}$`+`$\frac{1}{4}$`+`$\frac{1}{6}$`+...`$\frac{1}{50}$`)
=(`1`+`$\frac{1}{3}$`+`$\frac{1}{5}$`+...+`$\frac{1}{50}$`) - (`$\frac{1}{2}$`+`$\frac{1}{3}$`+`$\frac{1}{5}$`+...`$\frac{1}{25}$`)
=`$\frac{1}{26}$`+`$\frac{1}{27}$`+`$\frac{1}{28}$`+...+`$\frac{1}{50}$`
`XIN` `HAY` `NHẤT`
