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Gọi \(A=\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+...+\frac{1}{22.25}\)
\(\Leftrightarrow\)\(3A=\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{22.25}\)
\(\Leftrightarrow\)\(3A=\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{22}-\frac{1}{25}\)
\(\Leftrightarrow\)\(3A=1-\frac{1}{25}\)
\(\Leftrightarrow\)\(3A=\frac{24}{25}\)
\(\Leftrightarrow\)\(A=\frac{24}{25}:3\)
\(\Leftrightarrow\)\(A=\frac{24}{25}.\frac{1}{3}\)
\(\Leftrightarrow\)\(A=\frac{8}{25}\)
Vậy \(A=\frac{8}{25}\)
Đặt \(C=\frac{1}{1.4}+\frac{1}{4.7}+...+\frac{1}{22.25}\)
\(\Rightarrow3C=\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+....+\frac{3}{22.25}\)
\(\Rightarrow3C=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{22}-\frac{1}{25}\)
\(\Rightarrow3C=1-\frac{1}{25}=\frac{24}{25}\)
\(\Rightarrow C=\frac{24}{25}:3=\frac{8}{25}\)
Vậy \(\frac{1}{1.4}+\frac{1}{4.7}+...+\frac{1}{22.25}=\frac{8}{24}\)
bai nay de thui
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\(\frac{9}{15}< \frac{9}{17}\)
\(\frac{12}{25}=\frac{36}{75}\)
\(\frac{17}{15}< \frac{5}{4}\)
\(A=\frac{8\cdot4\cdot125\cdot25+96524+2476}{10\cdot125\cdot4\cdot25\cdot8}\)
\(A=\frac{1+96524+2476}{10}\)
\(A=\frac{99001}{10}\)
\(B=\frac{5+55+555+5555}{9+99+999+9999}\)
\(B=\frac{9}{5}\)
1 1/5 x 1 1/6 x 1 1/7 x ... x 1 1/2006
= 6/5 x 7/6 x 8/7 x ... 2007/2006
= 1/5 x 1/2006
= 1/10030
Mình ko chắc đâu bạn! Nhưng mình vẫn chúc bạn hok tốt nha!
Bạn Crystal ơi, làm thế nào mà bạn ra được \(\frac{1}{5}\)vậy ạ?
\(=\frac{6}{5}\times\frac{7}{6}\times...\times\frac{11}{10}\)(lại lỗi đề)
\(=\frac{6×7×...×11}{5×6×...×10}\)
\(=\frac{11}{5}\)
\(1\frac{1}{5}\cdot1\frac{1}{6}\cdot1\frac{1}{7}\cdot1\frac{1}{8}\cdot1\frac{1}{9}\cdot1\frac{1}{10}\)
\(=\frac{6}{5}\cdot\frac{7}{6}\cdot\frac{8}{7}\cdot\frac{9}{8}\cdot\frac{10}{9}\cdot\frac{11}{10}\)
\(=\frac{6\cdot7\cdot8\cdot9\cdot10\cdot11}{5\cdot6\cdot7\cdot8\cdot9\cdot10}\)
\(=\frac{11}{5}\)
\(C=\frac{9}{10}-\frac{1}{10.9}-\frac{1}{9.8}-...-\frac{1}{3.2}-\frac{1}{2.1}\)
\(C=\frac{9}{10}-\left(\frac{1}{1.2}+\frac{1}{2.3}+....+\frac{1}{9.8}+\frac{1}{9.10}\right)\)
\(C=\frac{9}{10}-\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)
\(C=\frac{9}{10}-\left(\frac{1}{1}-\frac{1}{10}\right)\)
\(C=\frac{9}{10}-\frac{9}{10}=0\)
không nói linh tinh nha thánh troll trả lời thì trả lời đi bị trừ điểm đó
\(5\frac{3}{4}\times x=8\frac{2}{5}\)
\(\frac{23}{4}\times x=\frac{42}{5}\)
\(x=\frac{42}{5}\div\frac{23}{4}\)
\(x=\frac{168}{115}\)
\(5\frac{3}{4}.x=8\frac{2}{5}\)
\(\frac{23}{4}.x=\frac{42}{5}\)
\(x=\frac{42}{5}:\frac{23}{4}\)
\(x=\frac{168}{115}\)
vậy \(x=\frac{168}{115}\)
Bùi Thùy Linh
21/20 nha bam
k tui nha
thank
\(\frac{63.303}{505.36}=\frac{9.7.101.3}{101.5.9.4}=\frac{21}{20}\)
\(\frac{63.303}{505.36}=\frac{7.9.3.101}{5.101.4.9}=\frac{3.7}{5.4}=\frac{21}{20}\)
\(\frac{5}{28}.\frac{24}{25}.1\frac{17}{18}=\frac{6}{35}.\frac{35}{18}=\frac{6}{18}=\frac{1}{3}\)
\(\frac{63.303}{505.36}=\frac{7.9.101.3}{5.101.4.9}=\frac{21}{20}\)
\(\frac{5}{28}\cdot\frac{24}{25}\cdot1\frac{17}{18}\)
= \(\frac{5}{28}\cdot\frac{24}{25}\cdot\frac{35}{18}\)
= \(\frac{6}{35}\cdot\frac{35}{18}\)
= \(\frac{1}{3}\)
a) Ta có:
\(\frac{63\times303}{505\times36}=\frac{3^2.7.101.3}{101.5.3^2.2^2}=\frac{3^3.7.101}{2^2.3^2.5.101}=\frac{3.7.1}{4.1.5.1}=\frac{21}{20}\)
b) Ta có:
\(\frac{5}{28}\times\frac{24}{25}\times1\frac{17}{18}=\frac{5}{28}\times\frac{24}{25}\times\frac{35}{18}=\frac{5\times24\times35}{28\times25\times18}\)
\(=\frac{5\times2^3\times3\times5\times7}{2^2\times7\times5^2\times2\times3^2}=\frac{2^3\times3\times5^2\times7}{2^3\times3^2\times5^2\times7}=\frac{1\times1\times1\times1}{1\times3\times1\times1}=\frac{1}{3}\)
\(\frac{63.303}{505.36}=\frac{7.9.3.101}{5.101.9.4}=\frac{21}{20}\)
Bạn ơi bạn gạch chéo những số giống nhau nha.
\(\frac{5}{28}\cdot\frac{24}{25}\cdot1\frac{17}{18}=\frac{5}{28}\cdot\frac{24}{25}\cdot\frac{35}{18}\)\(=\frac{5.24.35}{28.25.18}=\frac{5.6.4.7.5}{7.4.5.5.6.3}=\frac{1}{3}\)
Câu này cũng gạch chéo những số giống nhau nha bạn.