10th Class Mathematics Polynomials Question Bank MCQs - Polynomials

  • question_answer
    If \[\alpha \] and \[\beta \]are zeroes of the polynomial \[{{x}^{2}}-p\left( x+1 \right)+c\]such that \[\left( \alpha +1 \right)\left( \beta +1 \right)=0\], then the value of c is

    A) -2

    B) 2

    C) -1

    D) 1

    Correct Answer: C

    Solution :

    Given, \[\alpha \] and \[\beta \]are the zeroes of polynomial
    \[{{x}^{2}}-p\left( x+1 \right)+c\]which can be written as
    \[{{x}^{2}}-px+c-p\].
    So, sum of zeroes, \[\alpha +\beta =p\]              ... (i)
    \[\left[ \because \,\,sum\,of\,zeroes=\frac{-\,coefficient\,of\,x}{coefficient\,\,of\,\,{{x}^{2}}} \right]\]
    and product of zeroes, \[\alpha \beta =c-p\]      … (ii)
    \[\left[ \because \,\,product\,of\,zeroes=\frac{cons\tan t\,term}{coefficient\,of\,{{x}^{2}}} \right]\]
    Also,\[\left( \alpha +1 \right)\left( \beta +1 \right)=0\]        [given]
    \[\Rightarrow \,\,\alpha \beta +\left( \alpha +\beta  \right)+1=0\]
    \[\Rightarrow \,\,\alpha \beta +\left( \alpha +\beta  \right)+1=0\]0
    [from Eqs. (i) and (ii)]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,c=-1\]


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