Answer
$\displaystyle \ln\frac{9}{\sqrt{x^{2}+1}}$
Work Step by Step
See Th.5.2.
Property $1$ : $\ln(1)=0$
Property $2$ : $\ln(ab)=\ln a + \ln b$
Property $3$ : $\ln(a^{n})=n\cdot\ln a $
Property 4 : $\displaystyle \ln(\frac{a}{b})=\ln a - \ln b$
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$2\displaystyle \ln 3-\frac{1}{2}\ln(x^{2}+1)$= ... property $3$...
$=\ln 3^{2}-\ln(x^{2}+1)^{1/2}$= ... property $4$...
$=\displaystyle \ln\frac{9}{\sqrt{x^{2}+1}}$
