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![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{11}{9}+\frac{35}{18}\)
\(=\frac{19}{6}\)
\(\frac{22}{21}:\frac{1}{2}+\frac{25}{12}:\frac{1}{2}\)
\(\frac{44}{21}+\frac{25}{6}\)
\(\frac{263}{42}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:
\(B=\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)........\left(1-\frac{1}{2017}\right).\left(1-\frac{1}{2018}\right)\)
\(\Rightarrow B=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.......\frac{2016}{2017}.\frac{2017}{2018}\)
Đởn giản hết sẽ còn là:
\(\Rightarrow B=\frac{1}{2018}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(P=\frac{1}{5x8}+\frac{1}{8x11}+.....+\frac{1}{602x605}\)
\(\Rightarrow3P=\frac{3}{5x8}+\frac{3}{8x11}+......+\frac{3}{602x605}\)
\(\Rightarrow3P=\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-.....+\frac{1}{602}-\frac{1}{605}\)
\(\Rightarrow3P=\frac{1}{5}-\frac{1}{605}\)
\(\Rightarrow3P=\frac{24}{121}\)
\(\Rightarrow P=\frac{24}{121}:3\)
\(\Rightarrow P=\frac{8}{121}\)
\(\frac{22}{21}\): ( \(\frac{63}{4}\)\(-\frac{61}{4}\)) \(+\) \(\frac{25}{12}\): ( \(\frac{31}{4}\)\(-\)\(\frac{29}{4}\))
= \(\frac{22}{21}\): \(\frac{1}{2}\)+ \(\frac{25}{12}\): \(\frac{1}{2}\)
= ( \(\frac{22}{21}\)+ \(\frac{25}{12}\) ) : \(\frac{1}{2}\)
= \(\frac{263}{84}\) : \(\frac{1}{2}\)
=\(\frac{263}{42}\)
\(1\frac{1}{21}:\left(15,75-15\frac{1}{4}\right)+2\frac{1}{12}:\left(7\frac{3}{4}-7,25\right)\)
=\(\frac{22}{21}:\left(\frac{63}{4}-\frac{61}{4}\right)+\frac{25}{12}:\left(\frac{31}{4}-\frac{29}{4}\right)\)
=\(\frac{22}{21}:\frac{1}{2}+\frac{25}{12}:\frac{1}{2}=\frac{22x2}{21}+\frac{25x2}{12}\)
=\(\frac{44}{21}+\frac{25}{6}=\frac{88+175}{42}=\frac{263}{42}\)