Ta có: \(5\cdot18-10\cdot27+15\cdot36\)
\(=5\cdot9\cdot2-5\cdot9\cdot2\cdot3+5\cdot9\cdot3\cdot4\)
\(=5\cdot9\cdot\left(2-2\cdot3+3\cdot4\right)\)
Ta có: \(10\cdot36-20\cdot54+30\cdot72\)
\(=10\cdot18\cdot2-10\cdot18\cdot2\cdot3+10\cdot18\cdot3\cdot4\)
\(=10\cdot18\cdot\left(2-2\cdot3+3\cdot4\right)\)
Ta có: \(\frac{5\cdot18-10\cdot27+15\cdot36}{10\cdot36-20\cdot54+30\cdot72}\)
\(=\frac{5\cdot9\cdot\left(2-2\cdot3+3\cdot4\right)}{10\cdot18\cdot\left(2-2\cdot3+3\cdot4\right)}=\frac{5}{10}\cdot\frac{9}{18}\)
\(=\frac12\cdot\frac12=\frac14\)
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