Ta có: \(\frac{1.2.5+3.4.5+4.8.20+7.14.350}{2.5.11+6.10.33+8.20.44+14.35.770}\)
\(\Leftrightarrow\frac{1.2.5+3.4.5+4.8.20+7.14.35.10}{2.5.11+2.1.2.5.33+4.2.20.44+14.35.77.10}\)
\(\Leftrightarrow\frac{1+3.4+8+7}{11+2.1.2.33+2.44+77}\)
\(\Leftrightarrow\frac{28}{308}=\frac{28:28}{308:28}=\frac{1}{11}\)