10/50+10/140+10/160+...+10/1736
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QUY TẮC ⇒ TÍNH ĐƯỢC KẾT QUẢ BẰNG BAO NHIÊU RỒI CỘNG THÊM 100.
G = \(\left(\dfrac{1313}{1414}+\dfrac{10}{160}\right)-\left(\dfrac{130}{140}-\dfrac{1515}{1616}\right)\)
= \(\left(\dfrac{13}{14}+\dfrac{1}{16}\right)-\left(\dfrac{13}{14}-\dfrac{15}{16}\right)\)
= \(\dfrac{13}{14}+\dfrac{1}{16}-\dfrac{13}{14}+\dfrac{15}{16}\)
= \(\dfrac{1}{16}+\dfrac{15}{16}=1\)
bn có thể kết bn với tớ ko. Nếu muốn tớ kết bn thì phải click cho tớ trước
a.(-2013).2014+1007.26
=(-2013).2.1007+1007.26
=(-4026).1007+1007.26
=1007.(-4026+26)
=1007.(-4000)
=-4028000
b.(1313/1414 + 10/160) - (130/140 - 1515/1616)
=(13/14+1/16)-(13/140-(1/16+15/16)
=13/14+1/16-13/14+15/16
=(13/14+13/14)-(1/16+15/16)
=26/14-16/16
=26/14-1
=26/14-14/14
=12/14
=6/7
ấn đúng cho mình nhé
\(\)\(\dfrac{10}{56}+\dfrac{10}{140}+...+\dfrac{10}{1400}\)
\(=\dfrac{5}{28}+\dfrac{5}{70}+...+\dfrac{5}{700}\)
\(=\dfrac{5}{3}\left(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{25}-\dfrac{1}{28}\right)\)
\(=\dfrac{5}{3}\left(\dfrac{1}{4}-\dfrac{1}{28}\right)\)
\(=\dfrac{5}{3}\cdot\dfrac{6}{28}=2\cdot\dfrac{5}{28}=\dfrac{10}{28}=\dfrac{5}{14}\)
\(=\dfrac{5}{28}+\dfrac{5}{70}+\dfrac{5}{130}+...+\dfrac{5}{700}\\ =\dfrac{5}{3}\left(\dfrac{3}{4\cdot7}+\dfrac{3}{7\cdot10}+\dfrac{3}{10\cdot13}+...+\dfrac{3}{25\cdot28}\right)\\ =\dfrac{5}{3}\left(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{25}-\dfrac{1}{28}\right)\\ =\dfrac{5}{3}\left(\dfrac{1}{4}-\dfrac{1}{28}\right)=\dfrac{5}{3}\cdot\dfrac{3}{14}=\dfrac{5}{14}\)
\(\frac{5}{28}+\frac{5}{70}+\frac{5}{130}+\frac{5}{208}+\frac{5}{304}=\frac{5}{3}.\left(\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+\frac{3}{13.16}+\frac{3}{16.19}\right)\)
\(=\frac{5}{3}.\left(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{16}-\frac{1}{19}\right)=\frac{5}{3}.\left(\frac{1}{4}-\frac{1}{19}\right)\)
\(=\frac{5}{3}.\frac{15}{74}=\frac{25}{74}\)
Sửa đề: \(\dfrac{10}{56}+\dfrac{10}{140}+\dfrac{10}{260}+...+\dfrac{10}{1736}\)
\(=\dfrac{5}{28}+\dfrac{5}{70}+\dfrac{5}{130}+...+\dfrac{5}{868}\)
\(=\dfrac{5}{4\cdot7}+\dfrac{5}{7\cdot10}+...+\dfrac{5}{28\cdot31}\)
\(=\dfrac{5}{3}\times\left(\dfrac{3}{4\times7}+\dfrac{3}{7\times10}+...+\dfrac{3}{28\times31}\right)\)
\(=\dfrac{5}{3}\times\left(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{28}-\dfrac{1}{31}\right)\)
\(=\dfrac{5}{3}\times\left(\dfrac{1}{4}-\dfrac{1}{31}\right)=\dfrac{5}{3}\times\dfrac{27}{124}=\dfrac{45}{124}\)
@ Nguyễn Lê Phước Thịnh
Thank anh/chị ạ !