Đặt \(a = {\log _3}5;b = lo{g_4}5\). Hãy biểu diễn \({\log _{15}}20\) theo a và b.
A. \({\log _{15}}20 = \frac{{a\left( {1 + a} \right)}}{{b\left( {a + b} \right)}}\)
B. \({\log _{15}}20 = \frac{{b\left( {1 + a} \right)}}{{a\left( {1 + b} \right)}}\)
C. \({\log _{15}}20 = \frac{{b\left( {1 + b} \right)}}{{a\left( {1 + a} \right)}}\)
D. \({\log _{15}}20 = \frac{{a\left( {1 + b} \right)}}{{b\left( {1 + a} \right)}}\)
A. \({\log _{15}}20 = \frac{{a\left( {1 + a} \right)}}{{b\left( {a + b} \right)}}\)
B. \({\log _{15}}20 = \frac{{b\left( {1 + a} \right)}}{{a\left( {1 + b} \right)}}\)
C. \({\log _{15}}20 = \frac{{b\left( {1 + b} \right)}}{{a\left( {1 + a} \right)}}\)
D. \({\log _{15}}20 = \frac{{a\left( {1 + b} \right)}}{{b\left( {1 + a} \right)}}\)