chứng minh rằng: 1/1.2+1/3.4+1/5.6+……+1/49.50=1/26+1/27+1/28+……+1/50

`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`