(1/4.9+1/9.14+…+1/44.49).(1-3-5-7-…-49)/89 21/09/2021 Bởi Alice (1/4.9+1/9.14+…+1/44.49).(1-3-5-7-…-49)/89
Đáp án: Giải thích các bước giải: `(1/4.9+1/9.14+…+1/44.49).(1-3-5-7-…-49)/89` `=(5/4.9+5/9.14+…+5/44.49).(2-(1+3+5+7+…+49))/89 . 1/5` `=(1/4-1/9+1/9-1/14+…+1/44-1/49) .(2-625)/89 . 1/5` `=(1/4 -1/49 ) . (-7) .1/5` `=(-9)/28` Bình luận
Đáp án+Giải thích các bước giải: $\\\left(\dfrac{1}{4.9}+\dfrac{1}{9.14}+\dfrac{1}{14.19}+…+\dfrac{1}{44.49}\right).\dfrac{1-3-5-7-….-49}{89}\\=\dfrac{1}{5}.\left(\dfrac{5}{4.9}+\dfrac{5}{9.14}+\dfrac{5}{14.19}+…+\dfrac{5}{44.49}\right).\dfrac{1-(3+5+7+….+49)}{89}\\=\dfrac{1}{5}.\left(\dfrac{1}{4}-\dfrac{1}{9}+\dfrac{1}{9}+\dfrac{1}{14}-\dfrac{1}{14}+…+\dfrac{1}{44}-\dfrac{1}{49}\right).\dfrac{\text{1-{(3+49).$[\left(\dfrac{49-3}{2}+1\right)$:2]}}}{89}\\=\dfrac{1}{5}.\left(\dfrac{1}{4}-\dfrac{1}{49}\right).\dfrac{-623}{89}\\=\dfrac{1}{5}.\dfrac{45}{196}.\dfrac{-623}{89}\\=\dfrac{-9}{28}$ Bình luận
Đáp án:
Giải thích các bước giải:
`(1/4.9+1/9.14+…+1/44.49).(1-3-5-7-…-49)/89`
`=(5/4.9+5/9.14+…+5/44.49).(2-(1+3+5+7+…+49))/89 . 1/5`
`=(1/4-1/9+1/9-1/14+…+1/44-1/49) .(2-625)/89 . 1/5`
`=(1/4 -1/49 ) . (-7) .1/5`
`=(-9)/28`
Đáp án+Giải thích các bước giải:
$\\\left(\dfrac{1}{4.9}+\dfrac{1}{9.14}+\dfrac{1}{14.19}+…+\dfrac{1}{44.49}\right).\dfrac{1-3-5-7-….-49}{89}\\=\dfrac{1}{5}.\left(\dfrac{5}{4.9}+\dfrac{5}{9.14}+\dfrac{5}{14.19}+…+\dfrac{5}{44.49}\right).\dfrac{1-(3+5+7+….+49)}{89}\\=\dfrac{1}{5}.\left(\dfrac{1}{4}-\dfrac{1}{9}+\dfrac{1}{9}+\dfrac{1}{14}-\dfrac{1}{14}+…+\dfrac{1}{44}-\dfrac{1}{49}\right).\dfrac{\text{1-{(3+49).$[\left(\dfrac{49-3}{2}+1\right)$:2]}}}{89}\\=\dfrac{1}{5}.\left(\dfrac{1}{4}-\dfrac{1}{49}\right).\dfrac{-623}{89}\\=\dfrac{1}{5}.\dfrac{45}{196}.\dfrac{-623}{89}\\=\dfrac{-9}{28}$