JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Relation between roots and coefficients

  • question_answer
    The condition that one root of the equation \[a{{x}^{2}}+bx+c=0\]is three times the other is [DCE  2002]

    A) \[{{b}^{2}}=8ac\]

    B) \[3{{b}^{2}}+16ac=0\]

    C) \[3{{b}^{2}}=16ac\]

    D) \[{{b}^{2}}+3ac=0\]

    Correct Answer: C

    Solution :

    Let the roots are a and 3a \ \[\alpha +3\alpha =\frac{-b}{a}\Rightarrow \alpha =-\frac{b}{4a}\] and \[\alpha .3\alpha =\frac{c}{a}\] Þ  \[\frac{c}{a}=3.\frac{{{b}^{2}}}{16{{a}^{2}}}\] Þ \[16ac=3{{b}^{2}}\].


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