72 : 3 = ?
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\(72\cdot3+72\cdot6+72=72\cdot\left(3+6+1\right)=72\cdot10=720\)
Bài làm:
\(\frac{3}{200}-\frac{3}{110}-\frac{3}{90}-\frac{3}{72}-\frac{3}{56}-...-\frac{3}{2}\)
\(=\frac{3}{200}-3\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{110}\right)\)
\(=\frac{3}{200}-3\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{10.11}\right)\)
\(=\frac{3}{200}-3\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{10}-\frac{1}{11}\right)\)
\(=\frac{3}{200}-3\left(1-\frac{1}{11}\right)\)
\(=\frac{3}{200}-\frac{30}{11}=-\frac{5967}{2200}\)
Học tốt!!!!
a) `1/2 xx 5/4 + 1/2 xx 3/4 + 1/2`
`=1/2 xx (5/4 + 3/4 + 1)`
`=1/2 xx 3`
`=3/2`
b) `72/95 xx 64/72 xx 95/72 xx 14/86 xx 72/64 xx 86/14`
`=(72xx64xx95xx14xx72xx86)/(95xx72xx72xx86xx64xx14)`
`= 1`.
\(\left(\sqrt[3]{\dfrac{1}{9}}+4\cdot\sqrt[3]{\dfrac{1}{72}}-\sqrt[3]{4}\right)\left(\sqrt[3]{72}+\sqrt[3]{96}+\sqrt[3]{128}\right)\)
\(=\left(\dfrac{1}{3}\cdot\sqrt[3]{3}+4\cdot\dfrac{1}{6}\cdot\sqrt[3]{3}-2\sqrt[3]{\dfrac{1}{2}}\right)\left(2\sqrt[3]{9}+2\sqrt[3]{12}+4\sqrt[3]{2}\right)\)
\(=\left(\sqrt[3]{3}-2\sqrt[3]{\dfrac{1}{2}}\right)\left(6\sqrt[3]{3}+2\sqrt[3]{12}+4\sqrt[3]{2}\right)\)
\(=6\cdot3+2\sqrt[3]{36}+4\sqrt[3]{6}-12\sqrt[3]{\dfrac{3}{2}}-4\sqrt[3]{6}-8\)
\(=10+12\sqrt[3]{\dfrac{1}{6}}-6\sqrt[3]{12}\)
72:3=24