KVPY Sample Paper KVPY Stream-SX Model Paper-23

  • question_answer
    Let \[({{x}_{0}},{{y}_{0}})\] be the solution of the following equations \[{{(2x)}^{\ln 2}}={{(3y)}^{\ln 3}},{{3}^{\ln x}}={{2}^{\ln y}},\] then \[{{x}_{0}}\]

    A) \[\frac{1}{6}\]

    B) \[\frac{1}{3}\]

    C) \[\frac{1}{2}\]

    D) \[6\]

    Correct Answer: C

    Solution :

    We have, \[{{\left( 2x \right)}^{ln\,2}}={{\left( 3y \right)}^{ln\,3}}\]\[\Rightarrow \,\,\,\,ln2\left( ln\,\,2+ln\,x \right)=ln\,3\left( ln\,3+ln\,y \right)\]
    \[\Rightarrow \,{{\left( ln\,\,2 \right)}^{2}}+ln\,2.\,ln\,x={{\left( ln\,3 \right)}^{2}}+ln\,3.lny\] ?? (i)              \[\Rightarrow \,\,\,\,\,\,{{3}^{ln\,x}}={{2}^{ln\,y}}\]
    \[\Rightarrow \,\,\,\,\,\,\,ln\,\,x\,In\,\,3=ln\,\,y\,ln\,\,2\] ?? (ii)
    From Eqs. (i) and (ii) , we get
    \[{{\left( ln\,2 \right)}^{2}}+In\,2.\,lnx\]\[={{\left( ln\,\,3 \right)}^{2}}+ln\,3\left( \frac{ln\,x.\,ln\,3}{ln\,2} \right)\]\[\begin{align}   & \Rightarrow \,\,{{\left( ln\,2 \right)}^{3}}+{{\left( ln\,2 \right)}^{2}}ln\,x={{\left( ln\,3 \right)}^{2}}ln\,2 \\  & +{{\left( ln\,3 \right)}^{2}}ln\,x \\ \end{align}\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,(\ln \,x)\,\,[{{(\ln \,3)}^{2}}-{{(\ln \,2)}^{2}}]\]\[=\ln \,2\,[{{(\ln \,2)}^{2}}-{{(\ln \,3)}^{2}}]\]\[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,ln\,\,x=-ln\,2\]
    \[\therefore \,\,\,\,\,\,\,x=\frac{1}{2}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner