JEE Main & Advanced Sample Paper JEE Main - Mock Test - 38

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

    A) \[\frac{c(a-b)}{{{a}^{2}}}\]     

    B)        0

    C) \[\frac{-bc}{{{a}^{2}}}\]        

    D)        abc

    Correct Answer: A

    Solution :

    Given, \[{{\operatorname{ax}}^{2}}+bx+ c = 0\] and a, P are roots of given equation \[\therefore \,\,\,\alpha +\beta =-\frac{b}{a}\,\,and\,\,\alpha \beta =\frac{c}{a}\]                   ... (i) Now \[\alpha {{\beta }^{2}}+ {{\alpha }^{2}}\beta  + \alpha \beta  = \alpha \beta \left( \beta  + \alpha  \right) + \alpha \beta \] \[=\,\,\frac{c}{a}.\left( -\frac{b}{a} \right)+\frac{c}{a}\]                     [Using equation (i)] \[=\,\,-\frac{cb}{{{a}^{2}}}+\frac{c}{a}\] \[\Rightarrow \,\,\,\frac{-cb+ac}{{{a}^{2}}}=\frac{c(a-b)}{{{a}^{2}}}\]


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