Find the value of $\frac{\log_59\log_75\log_37}{\log_2\sqrt{6}}+\frac{1}{\log_9\sqrt{6}}$ $ \textbf{(A) }2\qquad\textbf{(B) }3\qquad\textbf{(C) }4\qquad\textbf{(D) }6\qquad\textbf{(E) }7 $
Problem
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Tags: logarithms
Zimbalono
03.06.2014 14:13
SMOJ wrote: Find the value of $\frac{\log_59\log_75\log_37}{\log_2\sqrt{6}}+\frac{1}{\log_9\sqrt{6}}$ $ \textbf{(A) }-1\qquad\textbf{(B) }1\qquad\textbf{(C) }2\qquad\textbf{(D) }-1\text{ or }2\qquad\textbf{(E) }-1\text{ or }-2 $
$4$
SMOJ
03.06.2014 15:34
edited
wangth100
04.06.2014 00:00
Using the "chain rule" for logarithms which states that $ (\log_a b)(\log_b c) = \log_a c $, we have:
\[ \begin{aligned} \frac{\log_59\log_75\log_37}{\log_2\sqrt{6}}+\frac{1}{\log_9\sqrt{6}} & = \frac{\log_37\log_75\log_59}{\log_2\sqrt{6}}+\frac{1}{\log_9\sqrt{6}} \\ & = \frac{\log_39}{\log_2\sqrt{6}}+\frac{1}{\log_9\sqrt{6}} \\ & = \frac{2}{\log_2\sqrt{6}}+\frac{1}{\log_9\sqrt{6}} \\ & = \frac{2}{\frac{1}{\log_{\sqrt{6}} 2}} + \frac{1}{\frac{1}{\log_{\sqrt{6}} 9}} \\ & = 2\log_{\sqrt{6}} 2 + \log_{\sqrt{6}} 9 \\ & = \log_{\sqrt{6}} 4 + \log_{\sqrt{6}} 9 \\ & = \log_{\sqrt{6}} 36 \\ & = \boxed{4} .\end{aligned} \]