Railways Quantitative Aptitude Power, Surds And Indices Sample Paper Surds Indices Sample Test Paper-4

  • question_answer
    If \[{{\left[ {{\left\{ {{\left( \frac{1}{{{7}^{2}}} \right)}^{-2}} \right\}}^{-1/3}} \right]}^{\frac{1}{4}}}={{7}^{m}},\] then find the value of m.

    A)  \[m=1\]           

    B)  \[m=\frac{1}{3}\]

    C)  \[m=-\frac{1}{3}\]       

    D)  \[m=-7\]

    Correct Answer: C

    Solution :

    [c] \[{{\left[ {{\left\{ {{\left( \frac{1}{{{7}^{2}}} \right)}^{-2}} \right\}}^{\frac{-1}{3}}} \right]}^{\frac{1}{4}}}={{7}^{m}}\] \[\Rightarrow \] \[{{\left[ {{\{{{({{7}^{-2}})}^{-2}}\}}^{-1/3}} \right]}^{\frac{1}{4}}}={{7}^{m}}\] \[\Rightarrow \] \[{{\left[ {{({{7}^{4}})}^{-1/3}} \right]}^{\frac{1}{4}}}={{7}^{m}}\] \[\Rightarrow \] \[{{({{7}^{-4/3}})}^{1/4}}={{7}^{m}}\] \[\Rightarrow \] \[{{7}^{-1/3}}={{7}^{m}}\] \[\therefore \] \[m=-1/3\]


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