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B1:A=2.17.12+4.6.21+8.3.62
A=(2.12).17+(4.6).21+(8.3).62
A=24.17+24.21+24.62
A=24.(17+21+62)
A=24.100
A=2400
B2:
B=37.24+37.76+63.79+63.21
B=37(24+76)+63(79+21)
B=37.100+63.100
B=100.(63+37)
B=100.100
B=10000
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\(=5.22\left(3134+275\cdot2+1.079\cdot4\right)\)
\(=5.22\cdot3688.316=19253.00952\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(1\dfrac{13}{15}.0,75-\left(\dfrac{11}{20}+25\%\right):\dfrac{3}{7}\)
\(\Leftrightarrow\) \(\left\{{}\begin{matrix}=\dfrac{28}{15}.\dfrac{3}{4}-\left(\dfrac{11}{20}+\dfrac{1}{4}\right):\dfrac{7}{3}\\=\dfrac{7}{5}-\dfrac{4}{5}.\dfrac{3}{7}\\=\dfrac{7}{5}-\dfrac{12}{35}\\=\dfrac{37}{35}\end{matrix}\right.\)\(\Rightarrow\) \(kết\) \(quả\) \(=\dfrac{37}{35}\)
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\(\Rightarrow C=\left(-\dfrac{3}{4}\right)\cdot\left(-\dfrac{8}{9}\right)\cdot\left(-\dfrac{15}{16}\right)\cdot\cdot\cdot\cdot\left(-\dfrac{399}{400}\right)\)
\(=-\left(\dfrac{3}{4}\cdot\dfrac{8}{9}\cdot\dfrac{15}{16}\cdot\cdot\cdot\cdot\dfrac{399}{400}\right)\)
\(=-\left(\dfrac{1\cdot3}{2\cdot2}\cdot\dfrac{2\cdot4}{3\cdot3}\cdot\dfrac{3\cdot5}{4\cdot4}\cdot\cdot\cdot\cdot\dfrac{19\cdot21}{20\cdot20}\right)\)
\(=-\left(\dfrac{1\cdot2\cdot3\cdot4\cdot...\cdot19}{2\cdot3\cdot4\cdot...\cdot20}\cdot\dfrac{3\cdot4\cdot5\cdot...\cdot21}{2\cdot3\cdot4\cdot...\cdot20}\right)\)
\(=-\left(\dfrac{1}{20}\cdot\dfrac{21}{2}\right)=-\dfrac{21}{40}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
g ) .
\(=10\dfrac{2}{9}+2\dfrac{2}{5}-7\dfrac{2}{9}=\left(10\dfrac{2}{9}-7\dfrac{2}{9}\right)+2\dfrac{2}{5}\)
\(=\left(\left(10-7\right)\left(\dfrac{2}{9}-\dfrac{2}{9}\right)\right)+\dfrac{12}{5}\)
\(=3+\dfrac{12}{5}=\dfrac{15}{5}+\dfrac{12}{5}=\dfrac{27}{5}\)
h ) .
\(=6\dfrac{3}{10}-3\dfrac{4}{7}-2\dfrac{3}{10}=\left(6\dfrac{3}{10}-2\dfrac{3}{10}\right)-3\dfrac{4}{7}\)
\(=\left(\left(6-2\right)\left(\dfrac{3}{10}-\dfrac{3}{10}\right)\right)-\dfrac{25}{7}\)
\(=4-\dfrac{25}{7}=\dfrac{28}{7}-\dfrac{25}{7}=\dfrac{3}{7}\)
g,92/9+12/5-65/9
=(92/9-65/9)+12/5
=3+12/5
=15/5+12/5
=27/5
h,=63/10-25/7-23/10
=(63/10-23/10)-25/7
=4-25/7
=28/7-25/7
=3/7
i,=67/9+51/11-31/9
=(67/9-31/9)+51/11
=4+55/11
=44/11+55/11
=99/11
=9
![](https://rs.olm.vn/images/avt/0.png?1311)
Đặt tổng trên là A
\(A=\left[\left(-37\right).86\right]+\left(37.76\right)\)
Áp dụng qui tắc dấu ngoặc, ta có:
\(A=\left[\left(-37\right)+37\right].\left(86+76\right)\)
\(A=0.\left(86+76\right)\)
\(A=0.162\)
\(A=0\)
Vậy A = 0
\(-37\times86+37\times76\)
\(=37\times\left(-86+76\right)\)
\(=37\times\left(-10\right)\)
\(=-370\)