10th Class Mathematics Polynomials Question Bank MCQs - Polynomials

  • question_answer
    If \[\alpha ,\beta ,\gamma \] are the zeroes of the polynomial \[f(x)={{x}^{3}}-a{{x}^{2}}+bx-c,\]then\[\frac{1}{\alpha \beta }+\frac{1}{\beta \gamma }+\frac{1}{\gamma \alpha }=\]

    A) \[\frac{c}{a}\]

    B) \[\frac{a}{c}\]

    C) \[-\frac{a}{c}\]

    D) \[-\frac{c}{a}\]

    Correct Answer: B

    Solution :

    [b] Since \[\alpha ,\beta ,\gamma \] are the zeroes of the polynomial
    \[f(x)={{x}^{3}}-a{{x}^{2}}+bx-c.\]
    \[\therefore \,\,\,\,\,\alpha +\beta +\gamma =-\frac{(-a)}{1}=a,\] \[\alpha \beta \gamma =-\frac{(-c)}{1}=c\]
    Now, \[\frac{1}{\alpha \beta }+\frac{1}{\beta \gamma }+\frac{1}{\gamma \alpha }=\frac{\alpha +\beta +\gamma }{\alpha \beta \gamma }=\frac{a}{c}\]


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