CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2002

  • question_answer
    If \[{{\log }_{2}}7=x,\]then \[x\]is:

    A)  a rational number such that \[0<x<2\]

    B)  an rational number

    C)  a rational number such that \[2<x<3\]

    D)  a prime number of the form \[7x+2\]

    Correct Answer: B

    Solution :

    Suppose of possible \[{{\log }_{2}}7\]is rational say \[\frac{p}{q}\] where \[p\]and \[q\] are integers prime to each other then \[\frac{p}{q}={{\log }_{2}}7\Rightarrow {{2}^{p/q}}\Rightarrow {{2}^{p}}={{7}^{q}}.\] This is false because- L.H.S. is even where as the R.H.S. is odd.


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