Let $\left(x_0, y_0\right)$ be the solution of the following equations $(2 x)^{\ln 2}=(3 y)^{\ln 3}$,…

Let $\left(x_0, y_0\right)$ be the solution of the following equations $(2 x)^{\ln 2}=(3 y)^{\ln 3}$, $3^{\ln x}=2^{\ln y}$, then $x_0$ is equal to
  1. $\frac{1}{6}$
  2. $\frac{1}{3}$
  3. $\frac{1}{2}$
  4. 6

Solution

Taking ln on both sides, $\ln 2 \cdot \ln (2 x)=\ln 3(\ln 3 y)$ $\begin{array}{ll} \Rightarrow & \ln 2\{\ln 2+\ln x\} \\ & =\ln 3\{\ln 3+\ln y\} \\ \text { and } & \ln x \cdot \ln 3=\ln y \ln 2 \\ & \ln y=\frac{\ln x \cdot \ln 3}{\ln 2} \end{array}$ From Eqs. (i) and (ii), we get $\begin{aligned} & \ln 2\{\ln 2+\ln x\} \\ &=\ln 3 \cdot\left\{\ln 3+\frac{\ln x \cdot \ln 3}{\ln 2}\right\} \\ & \Rightarrow(\ln 2)^2+\ln 2 \cdot \ln x \\ &=(\ln 3)^2+\frac{(\ln 3)^2}{(\ln 2)} \cdot \ln x \\ & \Rightarrow \ln x\left\{\frac{(\ln 3)^2}{\ln 2}-\ln 2\right\} \\ &=(\ln 2)^2-(\ln 3)^2 \end{aligned}$ $\begin{aligned} & \Rightarrow \ln x=-\ln 2=\ln 2^{-1} \\ & \therefore x=\frac{1}{2} \end{aligned}$

Asked in: JEE Advanced 2011 (Paper 1)

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