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a,\(\left(\dfrac{-2}{3}+\dfrac{3}{7}\right):\dfrac{4}{5}+\left(\dfrac{-1}{3}+\dfrac{4}{7}\right):\dfrac{4}{5}\)
\(=\left(-\dfrac{2}{3}+\dfrac{3}{7}\right).\dfrac{5}{4}+\left(\dfrac{-1}{3}+\dfrac{4}{7}\right).\dfrac{5}{4}\)
\(=\left(\dfrac{-2}{3}+\dfrac{3}{7}+\dfrac{-1}{3}+\dfrac{4}{7}\right).\dfrac{5}{4}\)
\(=\left(-1+1\right).\dfrac{5}{4}=0\)
Chúc bạn học tốt!!!
Câu b làm tương tự!
a) Đoàn Đức Hiếu
b) \(\dfrac{5}{9}:\left(\dfrac{1}{11}-\dfrac{5}{22}\right)+\dfrac{5}{9}:\left(\dfrac{1}{15}-\dfrac{2}{3}\right)\)
\(=\dfrac{5}{9}:\left(-\dfrac{3}{22}\right)+\dfrac{5}{9}:\left(-\dfrac{3}{5}\right)\)
\(=-\dfrac{5}{9}\cdot\dfrac{22}{3}-\dfrac{5}{9}\cdot\dfrac{5}{3}\)
\(=-\dfrac{110}{27}-\dfrac{25}{27}\)
\(=-5\)
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A = \(\dfrac{2}{3.5}\) + \(\dfrac{2}{5.7}\) + \(\dfrac{2}{7.9}\) + ... + \(\dfrac{2}{19.21}\)
A = \(\dfrac{1}{3}\) - \(\dfrac{1}{5}\) + \(\dfrac{1}{5}\) - \(\dfrac{1}{7}\) + \(\dfrac{1}{7}\) - \(\dfrac{1}{9}\) + ... + \(\dfrac{1}{19}\) - \(\dfrac{1}{21}\)
A = \(\dfrac{1}{3}\) - \(\dfrac{1}{21}\)
A = \(\dfrac{2}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(25\frac{4}{9}-14\frac{6}{13}\right)-\left(24\frac{7}{13}-15\frac{5}{9}\right)\)
\(=\left(24\frac{7}{13}-14\frac{6}{13}\right)-\left(25\frac{4}{9}-15\frac{5}{9}\right)\)
\(=\frac{131}{13}-\frac{89}{9}\)
\(=\frac{22}{117}\)
🤦♀️ banj ghi lần phần gõ công thức trực quan đko??