8th Class Mathematics Related to Competitive Exam Question Bank Logarithms

  • question_answer
    If \[{{\mathbf{2}}^{\mathbf{lo}{{\mathbf{g}}_{\mathbf{3}}}\mathbf{9}}}\mathbf{+2}{{\mathbf{5}}^{\mathbf{lo}{{\mathbf{g}}_{\mathbf{9}}}\mathbf{3}}}\mathbf{=}{{\mathbf{8}}^{\mathbf{lo}{{\mathbf{g}}_{\mathbf{x}}}\mathbf{9}}}\mathbf{,}\] then x = ________.

    A)  9                    

    B)  8

    C)  3                                

    D)  2

    Correct Answer: B

    Solution :

    (b): \[{{2}^{lo{{g}_{3}}^{9}}}+{{25}^{lo{{g}_{9}}^{3}}}={{8}^{{{\log }_{x}}^{9}}}\] \[\Rightarrow {{2}^{log}}{{^{_{3}3}}^{^{2}}}+{{25}^{{{\log }_{{{3}^{2}}}}3}}={{8}^{{{\log }_{x}}9}}\] \[\Rightarrow {{2}^{2}}+{{25}^{1/2}}={{8}^{{{\log }_{x}}9}}\] \[\Rightarrow 9={{8}^{{{\log }_{x}}9}}\] \[\Rightarrow {{\log }_{x}}9={{\log }_{8}}9\] \[\Rightarrow x=8\].


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