Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
giữ lời ko làm chó
gọi A = 6 / ( 5*8 ) + ... + 198 / ( 101 * 200 )
=> A / 2 = 3 / ( 5*8 ) + 11 / ( 8 * 19 ) + ... + 99 / ( 101*200 )
A / 2 = 1/5 - 1/8 + 1/8 - 1/11 + ... + 1 / 101 - 1 / 200
A / 2 = 1/ 5 -1 / 200
A / 2 = 39 /200
A = 39 / 100
đã làm bài này rồi , đúng, giờ thì k hộ cái , ko giết đấy
\(A=\frac{6}{5.8}+\frac{22}{8.19}+\frac{24}{19.31}+\frac{140}{31.101}+\frac{198}{101.200}\)
\(\Rightarrow A=\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{19}+\frac{1}{19}-\frac{1}{31}+\frac{1}{31}-\frac{1}{101}+\frac{1}{101}-\frac{1}{200}\)
\(\Rightarrow A=\frac{1}{5}-\frac{1}{200}\)
\(\Rightarrow A=\frac{39}{200}\)
\(=2.\left(\frac{3}{5.8}+\frac{11}{8.19}+...+\frac{99}{101.200}\right)\)
\(=2.\left(\frac{1}{5}-\frac{1}{200}\right)\)
\(=2.\frac{39}{200}=\frac{39}{100}\)
\(E=\frac{6}{5.8}+\frac{22}{8.19}+\frac{24}{19.31}+\frac{140}{31.101}+\frac{198}{101.200}\)
\(=2.\left(\frac{3}{5.8}+\frac{11}{8.19}+\frac{12}{19.31}+\frac{70}{31.101}+\frac{99}{101.200}\right)\)
\(=2\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{19}+\frac{1}{19}-\frac{1}{31}+\frac{1}{31}-\frac{1}{101}+\frac{1}{101}-\frac{1}{200}\right)\)
\(=2\left(\frac{1}{5}-\frac{1}{200}\right)\)
\(=2.\frac{39}{200}\)
\(=\frac{39}{100}\)
\(\frac{19}{20}-\frac{5}{6.7}-\frac{5}{7.8}-\frac{5}{8.9}-...-\frac{5}{59.60}\)
= \(\frac{19}{20}-\left(\frac{5}{6.7}+\frac{5}{7.8}+\frac{5}{8.9}+...+\frac{5}{59.60}\right)\)
= \(\frac{19}{20}-5\left(\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+...+\frac{1}{59.60}\right)\)
= \(\frac{19}{20}-5\left(\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+...+\frac{1}{59}-\frac{1}{60}\right)\)
= \(\frac{19}{20}-5\left(\frac{1}{6}-\frac{1}{60}\right)\)
= \(\frac{19}{20}-5.\frac{3}{20}\)
= \(\frac{19}{20}-\frac{3}{4}\) = \(\frac{1}{5}\)
\(A=\frac{6}{5.8}+\frac{22}{8.19}+\frac{24}{19.31}+\frac{140}{31.101}+\frac{198}{101.200}\)
\(A=2.\left(\frac{1}{5}-\frac{1}{8}\right)+2.\left(\frac{1}{8}-\frac{1}{19}\right)+2.\left(\frac{1}{19}-\frac{1}{31}\right)+2.\left(\frac{1}{31}-\frac{1}{101}\right)+2.\left(\frac{1}{101}-\frac{1}{200}\right)\)
\(A=2.\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{19}+\frac{1}{19}-\frac{1}{31}+\frac{1}{31}-\frac{1}{101}+\frac{1}{101}-\frac{1}{200}\right)\)
\(A=2.\left(\frac{1}{5}-\frac{1}{200}\right)\)
\(A=2.\frac{39}{200}\)
\(\Rightarrow A=\frac{39}{100}\)