\(\frac{1}{2.3}=\frac{1}{2}-\frac{1}{3}\) trong đó 3 = x ; 2 = x - 1
\(\frac{1}{\left(x-1\right)x}=\frac{1}{x-1}-\frac{1}{x}\)
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\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+...+\frac{2}{x\left(x-1\right)}=\frac{2007}{2009}\)
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+.....+\frac{2}{x\left(x-1\right)}=\frac{2007}{2009}\)
\(\frac{1}{3}+\frac{1}{6}+...+\frac{2}{x\left(x-1\right)}=\frac{2007}{2009}\)
x-left(frac{20}{11.13}+frac{20}{13.15}+frac{20}{15.17}+...+frac{20}{53.55}right)frac{3}{11}frac{7}{4}x.left(frac{33}{12}+frac{3333}{2020}+frac{333333}{303030}+frac{33333333}{42424242}right)22frac{1}{3}+frac{1}{6}+frac{1}{10}+frac{1}{15}+...+frac{2}{xleft(x-1right)}frac{2007}{2009}left(frac{1}{4}+frac{1}{8}+frac{1}{16}+frac{1}{32}+frac{1}{64}+frac{1}{128}+frac{1}{256}right).x1
Đọc tiếp
x-\(\left(\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\right)=\frac{3}{11}\)
\(\frac{7}{4}x.\left(\frac{33}{12}+\frac{3333}{2020}+\frac{333333}{303030}+\frac{33333333}{42424242}\right)=22\)
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}+...+\frac{2}{x\left(x-1\right)}=\frac{2007}{2009}\)
\(\left(\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}+\frac{1}{256}\right).x=1\)
tính nhanh :
a, \(\left[1+\frac{1}{2005}\right]x\left[1+\frac{1}{2006}\right]x\left[1+\frac{1}{2007}\right]x\left[1+\frac{1}{2008}\right]x\left[1+\frac{1}{2009}\right]\)
\(A=\left(6:\frac{3}{5}-1\frac{1}{6}x\frac{6}{7}\right):\left(4\frac{1}{5}x\frac{10}{11}+5\frac{2}{11}\right)\)\(B=\left(1-\frac{1}{2}\right)x\left(1-\frac{1}{4}\right)x.......x\left(1-\frac{1}{2015}\right)x\left(1-\frac{1}{2016}\right)\)
\(C=5\frac{9}{10}:\frac{3}{2}-\left(2\frac{1}{3}x4\frac{1}{2}-2x2\frac{1}{3}\right):\frac{7}{4}\)
M=\(\left(1-\frac{1}{3}\right)x\left(1-\frac{1}{6}\right)x\left(1-\frac{1}{10}\right)x\left(1-\frac{1}{15}\right)x\left(1-\frac{1}{21}\right)x\left(1-\frac{1}{28}\right)\)
a)\(\left(1-\frac{1}{2}\right)x\left(1-\frac{1}{3}\right)x\left(1-\frac{1}{4}\right)x\left(1-\frac{1}{5}\right)x......x\left(1-\frac{1}{18}\right)x\left(1-\frac{1}{19}\right)x\left(1-\frac{1}{20}\right)\)
b)\(1\frac{1}{2}x1\frac{1}{3}x1\frac{1}{4}x1\frac{1}{5}x......x1\frac{1}{2005}x1\frac{1}{2006}x1\frac{1}{2007}\)
\(\frac{\left(\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\right)\div\left(\frac{1}{6}+\frac{1}{10}-\frac{1}{15}\right)}{\left(\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+\frac{1}{5}\right)\div\left(\frac{1}{4}-\frac{1}{6}\right)}\)