KVPY Sample Paper KVPY Stream-SX Model Paper-8

  • question_answer
    Maximum value of the expression \[\frac{10{{x}^{12}}}{{{x}^{24}}+2{{x}^{12}}+3{{x}^{16}}+3{{x}^{8}}+1}\] is equal to-

    A) 1                                 

    B) 2

    C) 10                                

    D) not defined

    Correct Answer: A

    Solution :

    \[f(x)=\frac{10}{{{x}^{12}}+2+3{{x}^{4}}+\frac{3}{{{x}^{4}}}+\frac{1}{{{x}^{12}}}}\]\[=\frac{10}{{{x}^{12}}+3{{x}^{4}}+\frac{3}{{{x}^{4}}}+\frac{1}{{{x}^{12}}}+2}=\frac{10}{{{\left( {{x}^{4}}+\frac{1}{{{x}^{4}}} \right)}^{3}}+2}\]
    \[\because \,\,\,{{x}^{4}}+\frac{1}{{{x}^{4}}}\ge 2\]
    \[\Rightarrow {{\left( {{x}^{4}}+\frac{1}{{{x}^{4}}} \right)}^{3}}+2\ge 10\]
    \[\therefore \,\,\,f(x)\le \frac{10}{10}=1\]


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