10th Class Mathematics Polynomials Question Bank MCQs - Polynomials

  • question_answer
    If the zeroes of the quadratic polynomial \[a{{x}^{2}}+bx+c,\] \[c\ne 0\]are equal. then: (NCERT EXEMPLAR)

    A) c and a have opposite signs

    B) c and b have opposite signs

    C) c and a have the same sign

    D) c and b have the same sign

    Correct Answer: C

    Solution :

    [c] The zeroes of the given quadratic polynomial \[a{{x}^{2}}+bx+c\] where \[c\ne 0,\]are equal, if coefficient of \[{{x}^{2}}\]and constant term have the same sign i.e., c and a have the same sign. While b i.e.. coefficient of x can be positive or negative but not zero.
    Consider, (i)   \[{{x}^{2}}+4x+4=0\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,{{(x+2)}^{2}}=0\Rightarrow x=-2,-2\]
    and (ii)         \[{{x}^{2}}-4x+4=0\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,{{(x-2)}^{2}}=0\Rightarrow x=2,2\]


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