K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Các câu hỏi dưới đây có thể giống với câu hỏi trên
17 tháng 8 2016
1/2×3 + 2/3×5 + 3/5×8 + 4/8×12 + ... + 10/47×57
= 1/2 - 1/3 + 1/3 - 1/5 + 1/5 - 1/8 + 1/8 - 1/12 + ... + 1/47 - 1/57
= 1/2 - 1/57
= 57/114 - 2/114
= 55/114
DG
1
XO
20 tháng 7 2019
D = \(\frac{1}{2}+\frac{1}{14}+\frac{1}{35}+...+\frac{1}{434}\)
= \(2.\left(\frac{1}{4}+\frac{1}{28}+\frac{1}{70}+...+\frac{1}{868}\right)\)
= \(2.\frac{1}{3}.\left(\frac{3}{4}+\frac{3}{28}+\frac{3}{70}+...+\frac{3}{868}\right)\)
= \(\frac{2}{3}.\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{28.31}\right)\)
= \(\frac{2}{3}.\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{28}-\frac{1}{31}\right)\)
= \(\frac{2}{3}.\left(1-\frac{1}{31}\right)\)
= \(\frac{2}{3}.\frac{30}{31}\)
= \(\frac{20}{31}\)
E = \(\frac{2}{15}+\frac{3}{40}+\frac{11}{152}+\frac{13}{608}+\frac{25}{1824}+\frac{30}{4959}\)
= \(\frac{2}{3.5}+\frac{3}{5.8}+\frac{11}{8.19}+\frac{13}{19.32}+\frac{25}{32.57}+\frac{30}{57.87}\)
= \(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{19}+\frac{1}{19}-\frac{1}{32}+\frac{1}{32}-\frac{1}{57}+\frac{1}{57}-\frac{1}{87}\)
= \(\frac{1}{3}-\frac{1}{87}\)
= \(\frac{28}{87}\)
S
16
TH
1
19 tháng 7 2019
\(25\frac{2}{13}-\left(\frac{15}{17}+15\frac{2}{3}\right)=\frac{327}{13}-\left(\frac{15}{17}+\frac{47}{3}\right)\)
\(=\frac{327}{13}-\frac{844}{51}\)
\(=\frac{5705}{663}\)
\(\frac{5}{30}+\frac{15}{90}+\frac{250}{150}+\frac{350}{210}+\frac{45}{270}=\frac{1}{6}+\frac{1}{6}+\frac{5}{3}+\frac{5}{3}+\frac{1}{6}\)
\(=\frac{3}{6}+\frac{10}{3}\)
\(=\frac{1}{2}+\frac{10}{3}\)
\(=\frac{23}{6}\)
\(3\frac{1}{11}.\frac{27}{46}.1\frac{6}{17}.2\frac{4}{9}=\frac{34}{11}.\frac{27}{46}.\frac{23}{17}.\frac{22}{9}\)
\(=\frac{68}{9}.\frac{27}{34}\)
\(=6\)
8 tháng 3 2023
\(=\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}+\dfrac{1}{6}-\dfrac{1}{6}-\dfrac{1}{8}+\dfrac{1}{8}+\dfrac{1}{10}-\dfrac{1}{10}-\dfrac{1}{12}+\dfrac{1}{12}+\dfrac{1}{13}\)
=1/2+1/13
=15/26
\(\frac{2}{3.5}+\frac{3}{5.8}+\frac{11}{8.19}+\frac{13}{19.32}+\frac{25}{32.57}+\frac{30}{57.87}\)
=\(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{19}+\frac{1}{19}-\frac{1}{32}+\frac{1}{32}-\frac{1}{57}+\frac{1}{57}-\frac{1}{87}\)
= 1/3 - 1/87
= 28/87
ai giải giúp mk với