vậy 4A=4/2-4/4-4/6+...+4/46-4/48-4/50
4A=48/25
A=12/25
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1, Tính
a, \(\frac{5}{2\cdot4}\)+\(\frac{5}{4\cdot6}\)+\(\frac{5}{6\cdot8}\)+.......+\(\frac{5}{48\cdot50}\)
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tinh GTBT
\(F=\frac{4}{2\cdot4}+\frac{4}{4\cdot6}+\frac{4}{6\cdot8}+...+\frac{4}{2008\cdot2010}\)
(\(\frac{4}{2\cdot4}+\frac{4}{4\cdot6}+\frac{4}{6\cdot8}+.....+\frac{4}{4020\cdot4022}\)) \(\cdot x=2010\)
\(\frac{2}{2\cdot4}+\frac{2}{4\cdot6}+\frac{2}{6\cdot8}+..............+\frac{2}{x\cdot\left(x+2\right)}=\frac{4}{9}\)
\(\frac{5}{2\cdot4}+\frac{5}{4\cdot6}+\frac{5}{6\cdot8}+.......+\frac{5}{100\cdot102}\)
help me , please everyone
Cho \(A=1\cdot3\cdot5\cdot7\cdot...\cdot49\)
\(B=\frac{1\cdot2\cdot3\cdot...\cdot48\cdot49\cdot50}{2\cdot4\cdot6\cdot...\cdot48\cdot50}\)
\(C=\frac{26}{2}\cdot\frac{27}{2}\cdot...\cdot\frac{50}{2}\)
So sánh A,B và C
Rút gọn \(A=\frac{2\cdot4+4\cdot8+8\cdot12+12\cdot16+16\cdot20}{1\cdot2+2\cdot4+4\cdot6+6\cdot8+8\cdot10}\) ta được A=
B=\(\frac{1}{2\cdot4}+\frac{1}{4\cdot6}+\frac{1}{6\cdot8}+...+\frac{1}{96\cdot98}+\frac{1}{98\cdot100}\)
Please help me!!!!!!!!
Tính tổng 50 số hạng đầu tiên của dãy : \(\frac{1}{2\cdot4};\frac{1}{4\cdot6};\frac{1}{6\cdot8};\frac{1}{8\cdot10};...\)