Advertisements (Quảng cáo)
Tính:
a) \(\frac{1}{2}{\log _7}36 – {\log _7}14 – 3{\log _7}\sqrt[3]{{21}}\)
b) \(\frac{{{{\log }_2}24 – \frac{1}{2}{{\log }_2}72}}{{{{\log }_3}18 – \frac{1}{3}{{\log }_3}72}}\)
c) \(\frac{{{{\log }_2}4 + {{\log }_2}10}}{{{{\log }_2}20 + 3{{\log }_2}2}}\)
Hướng dẫn làm bài:
Advertisements (Quảng cáo)
a) \({\log _7}\sqrt {36} – {\log _7}14 – {\log _7}21 = {\log _7}\frac{1}{{49}} = – 2\)
b) \(\frac{{{{\log }_2}24 – {{\log }_2}\sqrt {72} }}{{{{\log }_3}18 – {{\log }_3}\sqrt[3]{{72}}}} = \frac{{{{\log }_2}{2^{\frac{3}{2}}}}}{{{{\log }_3}{3^{\frac{4}{3}}}}} = \frac{9}{8}\)
c) \(\frac{{{{\log }_2}24 – {{\log }_2}\sqrt {72} }}{{{{\log }_3}18 – {{\log }_3}\sqrt[3]{{72}}}} = \frac{{{{\log }_2}{2^{\frac{3}{2}}}}}{{{{\log }_3}{3^{\frac{4}{3}}}}} = \frac{9}{8}\).