8th Class Mathematics Related to Competitive Exam Question Bank Logarithms

  • question_answer
    If \[\mathbf{x}={{\mathbf{y}}^{x}},\mathbf{y}={{z}^{y}}\mathbf{and}\,\mathbf{z}={{\mathbf{x}}^{y}},\]then the value of xyz equal to:

    A)  -1                               

    B)  0              

    C)  1   

    D)  xyz

    Correct Answer: C

    Solution :

    (c): \[x={{y}^{x}},y={{z}^{y}},z={{x}^{y}}\] \[\Rightarrow x=lo{{g}_{y}}x,y={{\log }_{z}}y,z={{\log }_{x}}z\] \[\Rightarrow xyz=\left( lo{{g}_{y}}x \right)\times \left( lo{{g}_{z}}y \right)\times \left( lo{{g}_{x}}z \right)\]  \[\Rightarrow xyz=\left( \frac{\log x}{\log y}\times \frac{\log y}{\log z}\times \frac{\log z}{\log x} \right)=1.\]


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