KVPY Sample Paper KVPY Stream-SX Model Paper-28

  • question_answer
    Solution set of the inequality \[{{\log }_{3}}(x+2)(x+4)+{{\log }_{1/3}}(x+2)<\frac{1}{2}{{\log }_{\sqrt{3}}}7\]

    A) \[(-2,-1)\]

    B) \[(-2,3)\]

    C) \[(-1,3)\]

    D) \[(3,\infty )\]

    Correct Answer: B

    Solution :

    \[\left( x+2 \right)\left( x+4 \right)>0.x+2>0\Rightarrow x>-2.\]
    Now (1) can be written as
    \[{{\log }_{3}}\left( x+2 \right)\left( x+4 \right)-{{\log }_{3}}\left( x+2 \right)<\frac{\left( \log 7 \right)/2}{\left( \log 3 \right)/2}\]\[\Rightarrow \]\[{{\log }_{3}}\left( x+4 \right)<{{\log }_{3}}7\]\[\Rightarrow \]\[x+4<7\operatorname{or}\,x<3.\]


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