J & K CET Engineering J and K - CET Engineering Solved Paper-2006

  • question_answer
    If \[f(x)=\lambda {{e}^{-ax}}\,\,(a>0)\] for  \[0\le x<\infty \] is a probability density, then 'k is equal to

    A)  \[a\]              

    B)  \[{{a}^{2}}\]

    C)  \[1/a\]           

    D)  \[{{a}^{2}}\]                  

    Correct Answer: A

    Solution :

    Given, \[f(x)=\lambda {{e}^{-ax}},\] for \[0\le x<\infty \] and \[a>0\] \[\therefore \] \[\int_{0}^{\infty }{\lambda {{e}^{-ax}}=1}\] \[\Rightarrow \] \[\lambda \left[ \frac{{{e}^{-ax}}}{-a} \right]_{0}^{\infty }=1\] \[\Rightarrow \] \[\lambda \left[ 0+\frac{1}{a} \right]=1\] \[\Rightarrow \] \[\frac{\lambda }{a}=1\] \[\Rightarrow \] \[\lambda =a\]


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