\(1\frac{1}{3}×1\frac{1}{8}×1\frac{1}{15}×1\frac{1}{24}×......×1\frac{1}{99}\)
a)\(\left(1\frac{1}{3}\right)\left(1\frac{1}{8}\right)\left(1\frac{1}{15}\right)...\left(1\frac{1}{99}\right)\)
b)\(\left(1+\frac{1}{3}\right)\left(1+\frac{1}{8}\right)\left(1+\frac{1}{15}\right)\left(1+\frac{1}{24}\right)\left(1+\frac{1}{99}\right)\)
N = \(1\frac{1}{3}\times1\frac{1}{8}\times1\frac{1}{15}\times1\frac{1}{24}\times...\times1\frac{1}{99}\)
Cho dãy \(1\frac{1}{3};1\frac{1}{8};1\frac{1}{15};1\frac{1}{24};1\frac{1}{35};...\)
Tìm hỗn số thứ 99 và tính tích 99 hỗn số đó
\(1\frac{1}{30}:\left(24\frac{1}{6}-24\frac{1}{5}\right)-\frac{1\frac{1}{2}-\frac{3}{4}}{4x-\frac{1}{2}}=\left(-1\frac{1}{15}\right):\left(8\frac{1}{5}-8\frac{1}{3}\right)\)
\(1\frac{1}{30}:\left(24\frac{1}{6}-24\frac{1}{5}\right)-\frac{1\frac{1}{2}-\frac{3}{4}}{4x-\frac{1}{2}}=\left(-1\frac{1}{15}\right):\left(8\frac{1}{5}-8\frac{1}{3}\right)\)
\(\Rightarrow\frac{31}{30}:\left(\frac{145}{6}-\frac{121}{5}\right)-\frac{\frac{3}{2}-\frac{3}{4}}{4x-\frac{1}{2}}=\left(\frac{-16}{15}\right):\left(\frac{41}{5}-\frac{25}{3}\right)\)
\(\Rightarrow\frac{31}{30}:\left(\frac{725}{30}-\frac{726}{30}\right)-\frac{\frac{6}{4}-\frac{3}{4}}{4x-\frac{1}{2}}=\left(\frac{-16}{15}\right):\left(\frac{123}{15}-\frac{125}{15}\right)\)
\(\Rightarrow\frac{31}{30}:\frac{-1}{30}-\frac{\frac{3}{4}}{4x-\frac{1}{2}}=\frac{-16}{15}:\frac{-2}{15}\)
\(\Rightarrow\frac{31}{30}.\frac{30}{-1}-\frac{3}{4}:\left(4x-\frac{1}{2}\right)=\frac{-16}{15}.\frac{15}{-2}\)
\(\Rightarrow\left(-31\right)-\frac{3}{4}:\left(4x-\frac{1}{2}\right)=8\)
\(\Rightarrow\frac{3}{4}:\left(4x-\frac{1}{2}\right)=\left(-31\right)-8\)
\(\Rightarrow\frac{3}{4}:\left(4x-\frac{1}{2}\right)=\left(-39\right)\)
\(\Rightarrow4x-\frac{1}{2}=\frac{3}{4}:\left(-39\right)\)
\(\Rightarrow4x-\frac{1}{2}=\frac{3}{4}.\frac{-1}{39}\)
\(\Rightarrow4x-\frac{1}{2}=\frac{-1}{52}\)
\(\Rightarrow4x=\frac{-1}{52}+\frac{1}{2}\)
\(\Rightarrow4x=\frac{-1}{52}+\frac{26}{52}\)
\(\Rightarrow4x=\frac{25}{52}\)
\(\Rightarrow x=\frac{25}{52}:4\)
\(\Rightarrow x=\frac{25}{52}.\frac{1}{4}\)
\(\Rightarrow x=\frac{25}{208}\)
Vậy \(x=\frac{25}{208}\)
Chúc bn học tốt
1\(\frac{1}{3}\)x 1\(\frac{1}{8}\)x 1\(\frac{1}{15}\)x1 \(\frac{1}{24}\)x .....x 1\(\frac{1}{99}\)
\(=\frac{4}{3}.\frac{9}{8}.\frac{16}{15}.\frac{25}{24}...\frac{100}{99}\)
\(1\frac{1}{3}\times1\frac{1}{8}\times1\frac{1}{15}\times1\frac{1}{24}\times...\times1\frac{1}{99}\)
\(=\frac{4}{3}\times\frac{9}{8}\times\frac{16}{15}\times\frac{25}{24}\times...\times\frac{100}{99}\)
\(=\frac{2\times2}{1\times3}\times\frac{3\times3}{2\times4}\times\frac{4\times4}{3\times5}\times\frac{5\times5}{4\times6}\times...\times\frac{10\times10}{9\times11}\)
\(=\frac{2}{1}\times\frac{10}{11}\)
\(=\frac{20}{11}\)
tìm x biết : \(1\frac{1}{3}:\left(24\frac{1}{6}-24\frac{1}{5}\right)-\frac{1\frac{1}{2}-\frac{3}{4}}{4x-\frac{1}{2}}=\left(-1\frac{1}{15}\right):\left(8\frac{1}{5}-8\frac{1}{3}\right)\)
Bài 1:CMR:\(\frac{1}{4}+\frac{1}{5}+\frac{1}{6}+...+\frac{1}{15}<2\)
Bài 2: \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{x.\left(x+1\right)}=\frac{99}{101}\)
Bài 3:\(A=\frac{8}{9}.\frac{15}{16}.\frac{24}{25}.....\frac{2449}{2500}\)
Bài 4:CMR:\(1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{49}-\frac{1}{50}=\frac{1}{26}+\frac{1}{27}+\frac{1}{28}+...+\frac{1}{50}\)
Tìm x biết: \(1.\frac{1}{30}:\left(24.\frac{1}{6}-24.\frac{1}{5}\right)-\frac{1.\frac{1}{2}-\frac{3}{4}}{4.x-\frac{1}{2}}=\left(-1.\frac{1}{15}\right):\left(8.\frac{1}{5}-8.\frac{1}{3}\right)\)
Tìm x biết \(1\frac{1}{30}:\left(24\frac{1}{6}-24\frac{1}{5}\right)-\frac{1\frac{1}{2}-\frac{3}{4}}{4x-\frac{1}{2}}=\left(-1\frac{1}{15}\right):\left(8\frac{1}{5}-8\frac{1}{3}\right)\)