JCECE Engineering JCECE Engineering Solved Paper-2003

  • question_answer
    If\[{{x}^{2}}-3x+2\]be a factor of\[{{x}^{4}}-p{{x}^{2}}+q\], then \[(p,\,\,q)\]is equal to:

    A) \[(3,\,\,4)\]                        

    B) \[(4,\,\,5)\]

    C) \[(4,\,\,3)\]                        

    D) \[(5,\,\,4)\]

    Correct Answer: D

    Solution :

    Key Idea: If\[a{{x}^{2}}+bx+c\]is a factor of\[{{x}^{4}}+d{{x}^{2}}+e\], then the roots of the quadratic equation will satisfy the equation. Let          \[f(x)={{x}^{2}}-3x+2=0\] \[\Rightarrow \]               \[(x-2)(x-1)=0\] \[\Rightarrow \]               \[x=1,\,\,2\] Since, \[{{x}^{2}}-3x+2\] be the factor of\[{{x}^{4}}-p{{x}^{2}}+q=0\]. \[\therefore \]The value of \[x\] will satisfy it. \[\Rightarrow \]               \[1-p+q=0\]and\[16-4p+q=0\] \[\Rightarrow \]               \[p=5,\,\,q=4\]


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