KVPY Sample Paper KVPY Stream-SX Model Paper-12

  • question_answer
    If the inequality \[\frac{m{{x}^{2}}+3x+4}{{{x}^{2}}+2x+2}<5\] is satisfied for all \[x\in R,\]then

    A)  \[1<m<5\]

    B) \[-1<m<1\]

    C) \[-5<m<\frac{11}{24}\]

    D) \[m<\frac{71}{24}\]

    Correct Answer: D

    Solution :

    \[\because \]\[{{x}^{2}}+2x+2={{(x+1)}^{2}}+1>0\,\forall \,x\in \mathbf{R}\]
    \[\therefore \frac{m{{x}^{2}}+3x+4}{{{x}^{2}}+2x+2}<5\]
    \[\Rightarrow \]\[(m-5){{x}^{2}}-7x-6<0\,\forall \,x\in \mathbf{R}\]
    \[\Rightarrow \]\[m-5<0\]and\[D<0\Rightarrow m<5\]
    \[\operatorname{and}49+24\left( m-5 \right)<0\Rightarrow m<\frac{71}{24}\]


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