-4\11.2\5+6\11.-3\10
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a) \(\frac{-1}{21}+\frac{-1}{28}-\frac{-1}{21}-\frac{3}{14}\)
\(=\frac{-1}{21}+\frac{-1}{28}+\frac{1}{21}+\frac{-3}{14}\)
\(=\left(\frac{-1}{21}+\frac{1}{21}\right)+\left(\frac{-1}{28}+\frac{-3}{14}\right)\)
\(=0+\left(\frac{-1}{28}+\frac{-6}{28}\right)\)
\(=0+\frac{-1}{4}=\frac{-1}{4}\)
b) \(\left(\frac{-1}{5}+\frac{3}{12}\right)+\frac{-3}{4}\)
\(=\frac{-1}{5}+\frac{1}{4}+\frac{-3}{4}\)
\(=\left(\frac{1}{4}+\frac{-3}{4}\right)+\frac{-1}{5}\)
\(=\frac{-1}{2}+\frac{-1}{5}\)
\(=\frac{-5}{10}+\frac{-2}{10}=\frac{-7}{10}\)
c) \(\frac{-4}{11}\cdot\frac{2}{5}+\frac{6}{11}\cdot\frac{-3}{10}\)
\(=\frac{-8}{55}+\frac{-9}{55}=\frac{-17}{55}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 1 dễ mà :
1.2.3...9 - 1.2.3...8 - 1.2.3...7.82
= 1.2.3...8.9 - 1.2.3...8.1 - 1.2.3...7.8.8
= 1.2.3...8.( 9 - 1 - 8 )
= 1.2.3...8.0
= 0
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YẾN ƠI TUI BẠN BÀ NÈ
NHƯNG TUI HỔNG PHẢI LỚP 6 THÔNG CẢM NHA
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\(\frac{3.7.8.13}{14\cdot15\cdot26}=\frac{3\cdot7\cdot8\cdot13}{2\cdot7\cdot3\cdot5\cdot2\cdot13}=\frac{8}{5\cdot2\cdot2}=\frac{8}{20}=\frac{2}{5}\)
\(\frac{3.7.8.13}{14.15.26}=\frac{3.7.2^3.13}{2.7.3.5.13.2}=\frac{1.7.2.1}{1.1.1.5.1.1}=\frac{14}{5}\)
\(\frac{11.8-11.3}{17-6}=\frac{11.\left(8-3\right)}{11}=\frac{11.5}{11}=\frac{1.5}{1}=\frac{5}{1}=5\)
\(\frac{-17.13+17.2}{11.2-11.9}=\frac{-17.13+\left(-17\right).2}{11.\left(2-9\right)}=\frac{-17.\left(-13+2\right)}{11.\left(-7\right)}=\frac{-17.\left(-11\right)}{11.\left(-7\right)}=\frac{-17.\left(-1\right)}{-1.\left(-7\right)}=\frac{17}{7}\)
\(\frac{7}{9.10^2-2.10^2}=\frac{7}{100\left(9-2\right)}=\frac{7}{100.7}=\frac{7}{700}=\frac{1}{100}\)
mình làm được tới đó thôi, hihi.
\(-\frac{4}{11}.\frac{2}{5}+\frac{6}{11}.\frac{-3}{10}\)
\(=\frac{-8}{55}+\frac{-9}{55}\)
\(=\frac{-17}{55}\)