10th Class Mathematics Related to Competitive Exam Question Bank Algebra

  • question_answer
    If \[\alpha \] and \[\beta \] be the roots of the equation \[{{x}^{2}}+px+q=0\], then the equation whose roots are \[{{\alpha }^{2}}+\alpha \beta \]and \[{{\beta }^{2}}+\alpha \beta \]is

    A)  \[{{x}^{2}}+{{p}^{2}}x+{{P}^{2}}q=0\]

    B)  \[{{x}^{2}}-{{q}^{2}}x+{{P}^{2}}q=0\]

    C)  \[{{x}^{2}}+{{q}^{2}}x+{{P}^{2}}q=0\]

    D)  \[{{x}^{2}}-{{p}^{2}}x+{{P}^{2}}q=0\]  

    Correct Answer: D

    Solution :

     Since \[\alpha \] and \[\beta \] are roots of the equation\[{{x}^{2}}+px+q=0\], therefore                 \[\alpha +\beta =-p\]                                     ? (i) and        \[\alpha \beta =q\]                                                         ? (ii) Sum of the roots \[={{\alpha }^{2}}+\alpha \beta +{{\beta }^{2}}+\alpha \beta \]                                 \[=(\alpha +\beta )={{p}^{2}}\] Product of the roots\[=(\alpha +\alpha \beta )({{\beta }^{2}}+\alpha \beta )\]                                     \[=\alpha \beta {{(\alpha +\beta )}^{2}}=q{{p}^{2}}\] Required equation will be \[{{x}^{2}}-\](Sum of the roots) \[x+\] Product of the roots \[=\,\,0\] or            \[{{x}^{2}}-{{p}^{2}}x+q{{p}^{2}}=0\]


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