JEE Main & Advanced Sample Paper JEE Main Sample Paper-44

  • question_answer
    The range of the function \[f(x)=[{{4}^{x}}-{{2}^{x+1}}+1],\] is, where [.] denotes greatest integer function

    A)  positive integers                       

    B)  whole numbers

    C)  prime numbers                        

    D)  all integers

    Correct Answer: B

    Solution :

     \[f(x)=[{{4}^{x}}-{{2}^{x+1}}+1],\] Let \[{{2}^{x}}=t\] \[[{{t}^{2}}-2t+1]\] \[=[{{(t-1)}^{2}}]=\,[{{({{2}^{x}}-1)}^{2}}]\] If \[x=0,\] then \[f(x)=0\] Otherwise, \[{{({{2}^{x}}-1)}^{2}}\] is always greater than zero, so range is \[x\,\,\in \,\,\{0,\,1,\,\,2,\,\,3,...\}\] i.e, the set of the whole numbers.


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