SSC Sample Paper SSC CHSL (10+2) Sample Test Paper-21

  • question_answer
    If\[2x+\frac{1}{3x}=3,\], then\[9{{x}^{2}}+\frac{1}{4{{x}^{2}}}=?\]?

    A)  \[16.25\]                      

    B)  \[17.25\]

    C)  18                               

    D)  17

    Correct Answer: B

    Solution :

     \[2x+\frac{1}{3x}=3\] Multiply both side by \[\frac{3}{2},\] \[2x\times \frac{3}{2}+\frac{3}{2}\times \frac{1}{3x}=3\times \frac{3}{2}\,\,3x+\frac{1}{2x}=\frac{9}{2}\] Taking square of both side- \[{{\left( 3x+\frac{1}{2x} \right)}^{2}}={{\left( \frac{9}{2} \right)}^{2}}\Rightarrow 9{{x}^{2}}+\frac{1}{4{{x}^{2}}}+2\times 3x\times \frac{1}{2x}\] \[=\frac{81}{4}\Rightarrow 9{{x}^{2}}+\frac{1}{4{{x}^{2}}}=\frac{81}{4}-3\Rightarrow \frac{81-12}{4}\] \[\underline{\mathbf{=17}\mathbf{.25}}\]


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