Đáp án:
C
Giải thích các bước giải:
Ta có: \(\log_215=\log_23+\log_25=a\)
\(\to a-\log_25=\log_23\)
\(\log_530=\log_56+\log_55\)
\(\to \log_530=\log_52+\log_53+1\)
\(\to\log_530=\log_52+\log_3+\log_52+1\)
\(\to\log_530=\log_52\left(1+a-\log_25\right)+1\)
\(\to\log_530=-\log_52.\log_25+\log_52\left(1+a\right)+1\)
\(\to\log_530=-1+1+\log_52(1+a)=b\)
\(\to \log_52=\dfrac b{1+a}\)
\(\to\log_23=a-\dfrac{1+a}b\)
\(\log_9225=\log_315\)
\(\to \log_9225=1+\log_35\)
\(\to \log_9225= 1+\dfrac{\log_25}{\log_23}\)
\(\to \log_9225=1+\dfrac{\dfrac{1+a}b}{a-\dfrac{1+a}b}\)
\(\to \log_9225=1+\dfrac{1+a}{ab-a-1}\)
\(\to \log_9225=\dfrac{ab}{ab-a-1}\)
\(\to\)Chọn C
