M=$\frac{3}{5.7}$ + $\frac{3}{7.9}$ +…+ $\frac{3}{59.61}$ 26/09/2021 Bởi Kennedy M=$\frac{3}{5.7}$ + $\frac{3}{7.9}$ +…+ $\frac{3}{59.61}$
Đáp án: Giải thích các bước giải: $M=\dfrac{3}{5.7}+\dfrac{3}{7.9}+…+\dfrac{3}{59.61}$ $ $ $=\dfrac{3}{2}.(\dfrac{2}{5.7}+\dfrac{2}{7.9}+…+\dfrac{3}{59.61})$ $ $ $=\dfrac{3}{2}.(\dfrac{1}{5}-\dfrac{1}{61})$ $ $ $=\dfrac{3}{2}.\dfrac{56}{305}$ $ $ $=\dfrac{84}{305}$ Bình luận
$M = \dfrac{3}{5.7}+ \dfrac{3}{7.9} + …. + \dfrac{3}{59.61}$ $⇔ M : 3 = \dfrac{1}{5.7}+ \dfrac{1}{7.9} + …. + \dfrac{1}{59.61}$ $⇔ M : 3 .2 = \dfrac{2}{5.7}+ \dfrac{2}{7.9} + …. + \dfrac{2}{59.61}$ $⇔M : \dfrac{3}{2} = \dfrac{1}{5} – \dfrac{1}{7} + \dfrac{1}{7} – \dfrac{1}{9} + …. + \dfrac{1}{59} – \dfrac{1}{61}$ $⇔ M : \dfrac{3}{2} = \dfrac{1}{5} – \dfrac{1}{61}$ $⇔ M : \dfrac{3}{2} = \dfrac{56}{305}$ $⇔ M =\dfrac{84}{305}$ Bình luận
Đáp án:
Giải thích các bước giải:
$M=\dfrac{3}{5.7}+\dfrac{3}{7.9}+…+\dfrac{3}{59.61}$
$ $
$=\dfrac{3}{2}.(\dfrac{2}{5.7}+\dfrac{2}{7.9}+…+\dfrac{3}{59.61})$
$ $
$=\dfrac{3}{2}.(\dfrac{1}{5}-\dfrac{1}{61})$
$ $
$=\dfrac{3}{2}.\dfrac{56}{305}$
$ $
$=\dfrac{84}{305}$
$M = \dfrac{3}{5.7}+ \dfrac{3}{7.9} + …. + \dfrac{3}{59.61}$
$⇔ M : 3 = \dfrac{1}{5.7}+ \dfrac{1}{7.9} + …. + \dfrac{1}{59.61}$
$⇔ M : 3 .2 = \dfrac{2}{5.7}+ \dfrac{2}{7.9} + …. + \dfrac{2}{59.61}$
$⇔M : \dfrac{3}{2} = \dfrac{1}{5} – \dfrac{1}{7} + \dfrac{1}{7} – \dfrac{1}{9} + …. + \dfrac{1}{59} – \dfrac{1}{61}$
$⇔ M : \dfrac{3}{2} = \dfrac{1}{5} – \dfrac{1}{61}$
$⇔ M : \dfrac{3}{2} = \dfrac{56}{305}$
$⇔ M =\dfrac{84}{305}$