JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Self Evaluation Test - Complex Numbers and Quadratic Equations

  • question_answer
    If the roots of the equation \[a{{x}^{2}}-bx+c=0\] are \[\alpha ,\beta \] then the roots of the equation \[{{b}^{2}}c{{x}^{2}}-a{{b}^{2}}x+{{a}^{3}}=0\] are

    A) \[\frac{1}{{{\alpha }^{3}}+\alpha \beta },\frac{1}{{{\beta }^{3}}+\alpha \beta }\]

    B) \[\frac{1}{{{\alpha }^{2}}+\alpha \beta },\frac{1}{{{\beta }^{2}}+\alpha \beta }\]

    C) \[\frac{1}{{{\alpha }^{4}}+\alpha \beta },\frac{1}{{{\beta }^{4}}+\alpha \beta }\]

    D) None of these

    Correct Answer: B

    Solution :

    Multiplying the second equation by \[\frac{c}{{{a}^{3}}}\], we get \[\frac{{{b}^{2}}{{c}^{2}}}{{{a}^{3}}}{{x}^{2}}-\frac{{{b}^{2}}c}{{{a}^{2}}}x+c=0\] \[\Rightarrow \,\,\,a{{\left( \frac{bc}{{{a}^{2}}}x \right)}^{2}}-b\left( \frac{bc}{{{a}^{2}}} \right)x+c=0\] \[\Rightarrow \,\,\,\frac{bc}{{{a}^{2}}}\,\,x=\alpha ,\,\,\beta \] \[\Rightarrow \,\,\,\,(\alpha +\beta )\alpha \beta x=\alpha ,\,\,\beta \] \[\Rightarrow \,\,x=\frac{1}{(\alpha +\beta )\alpha },\,\,\frac{1}{(\alpha +\beta )\beta }\]


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