RAJASTHAN ­ PET Rajasthan PET Solved Paper-2001

  • question_answer
    If difference of the roots of the equation \[{{x}^{2}}+px+8=0\]is 2, then value of p is

    A)  \[\pm 6\]              

    B)  \[\pm 2\]

    C)  \[2,-6\]             

    D)  \[6,2\]

    Correct Answer: A

    Solution :

     Let roots of the equation\[{{x}^{2}}+px+8=0\]are\[\alpha \]and\[\beta ,\]then \[\alpha +\beta =-p\] and         \[\alpha \beta =8\] Also given,   \[\alpha -\beta =2\] \[\Rightarrow \] \[\sqrt{{{(\alpha +\beta )}^{2}}-4\alpha \beta }=2\] \[\Rightarrow \] \[{{(-p)}^{2}}-4\times 8=4\] \[\Rightarrow \] \[{{p}^{2}}=4+32\] \[\Rightarrow \] \[p=\pm 6\]


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