BCECE Engineering BCECE Engineering Solved Paper-2002

  • question_answer
    If \[{{x}^{2}}+ax+\beta =0\]and \[{{x}^{2}}+px+q=0\] has a common roof, then the common root is:

    A) \[\frac{q+\beta }{a+p}\]                              

    B)  \[\frac{q-\beta }{a+p}\]              

    C)         \[\frac{q-\beta }{a-p}\]               

    D)                         none of these

    Correct Answer: C

    Solution :

    Let \[\alpha \]be the common root of the equations \[{{x}^{2}}+ax+\beta =0\]and \[{{x}^{2}}+px+q=0\] \[\Rightarrow \]\[{{\alpha }^{2}}+a\alpha +\beta =0\]and \[{{\alpha }^{2}}+p\alpha +q=0\] \[\therefore \] Both equations represents a same line \[\Rightarrow \]               \[\frac{{{\alpha }^{2}}}{aq-p\beta }=\frac{-\alpha }{q-\beta }=\frac{1}{p-a}\] \[\Rightarrow \]               \[\alpha =\frac{q-\beta }{a-p}\]


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