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Bài làm
\(D=\frac{6}{3,5}+\frac{6}{5.7}+...+\frac{6}{21.23}\)
\(D=3.\left(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{21.23}\right)\)
\(D=3.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{21}-\frac{1}{23}\right)\)
\(D=3.\left(\frac{1}{3}-\frac{1}{23}\right)\)
\(D=3.\frac{20}{69}\)
\(D=\frac{20}{23}\)
Học tốt
Bài làm
\(D=\frac{6}{3.5}+\frac{6}{5.7}+...+\frac{6}{21.23}\)
\(D=3.\left(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{21.23}\right)\)
\(D=3.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{21}-\frac{1}{23}\right)\)
\(D=3.\left(\frac{1}{3}-\frac{1}{23}\right)\)
\(D=3.\frac{20}{69}\)
\(D=\frac{20}{23}\)
\(E=\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\)
\(E=10.\left(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{53.55}\right)\)
\(E=10.\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)\)
\(E=10.\left(\frac{1}{11}-\frac{1}{55}\right)\)
\(E=10.\frac{4}{55}\)
\(E=\frac{8}{11}\)
\(G=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+...+\frac{1}{9900}\)
\(G=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{99.100}\)
\(G=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{99}-\frac{1}{100}\)
\(G=\frac{1}{1}-\frac{1}{100}\)
\(G=\frac{99}{100}\)
Nhớ k cho m nha
a) \(x-10\left(\frac{2}{15.17}+\frac{2}{17.19}+...+\frac{2}{73.75}\right)=\frac{7}{15}\)
\(x-10\left(\frac{1}{15}-\frac{1}{17}+\frac{1}{17}-\frac{1}{19}+...+\frac{1}{73}-\frac{1}{75}\right)=\frac{7}{15}\)
\(x-10\left(\frac{1}{15}-\frac{1}{75}\right)=\frac{7}{15}=>x-\frac{8}{15}=\frac{7}{15}=>x=1\)
b) \(x-10\left(\frac{2}{11.13}+\frac{2}{13.15}+...+\frac{2}{53.55}\right)=\frac{3}{11}\)
\(x-10\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}=>x-\frac{8}{11}=\frac{3}{11}=>x=1\)
A = \(\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+...+\frac{2}{97.100}\)
A= 2. ( \(\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+...+\frac{1}{97.100}\))
A= 2. ( \(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{97}-\frac{1}{100}\))
A= 2. (\(1-\frac{1}{100}\))
A= 2. \(\frac{99}{100}\)
A= \(\frac{99}{50}\)
ta có: \(1-\frac{5}{6}+\frac{7}{12}-\frac{9}{20}+\frac{11}{30}-\frac{13}{42}+\frac{15}{56}-\frac{17}{72}+\frac{19}{90}\)
\(=1-\frac{5}{2.3}+\frac{7}{3.4}-\frac{9}{4.5}+\frac{11}{5.6}-\frac{13}{6.7}+\frac{15}{7.8}-\frac{17}{8.9}+\frac{19}{9.10}\)
\(=1-\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{4}+\frac{1}{5}-\frac{1}{5}+\frac{1}{6}-\frac{1}{6}+\frac{1}{7}-\frac{1}{7}+\frac{1}{8}-\frac{1}{8}+\frac{1}{9}-\frac{1}{9}+\frac{1}{10}\)
\(=1-\frac{1}{2}+\frac{1}{10}=\frac{3}{5}\)
\(\frac{20}{8\cdot14}+\frac{20}{14\cdot20}+\frac{20}{20\cdot26}+\frac{20}{26\cdot32}\)\(\Rightarrow\frac{10}{3}\left(\frac{6}{8\cdot14}+\frac{6}{14\cdot20}+\frac{6}{20\cdot26}+\frac{6}{26+32}\right)\)
\(M=\frac{10}{3}\left(\frac{1}{8}-\frac{1}{14}+\frac{1}{14}-\frac{1}{20}+\frac{1}{20}-\frac{1}{26}+\frac{1}{26}-\frac{1}{32}\right)\)\(\Rightarrow M=\frac{10}{3}\left(\frac{1}{8}-\frac{1}{32}\right)=\frac{10}{3}\cdot\frac{3}{32}=\frac{10}{32}\)
k cho mình nha!
tat ca diem trung cua cac so nay la deu chia het cho 5 va co tu =nhau
so so hang la
(20/130-20/575):0,1+1=655/299
tong tat ca cac so la:
(20/130+20/575):2.655/299~0,2066