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9th Class Mathematics Polynomials Question Bank Polynomials

  • question_answer
    If \[\mathbf{x}+\mathbf{1}\text{ }\mathbf{and}\text{ }\mathbf{x}-\mathbf{1}\] are factors of \[\mathbf{f}\left( \mathbf{x} \right)\mathbf{=}{{\mathbf{x}}^{\mathbf{4}}}\mathbf{+3ax+b,}\] then the value of \[\mathbf{3a}+\mathbf{2b}\] is

    A)  5                                

    B)  -1  

    C)  4                                

    D)  -6

    Correct Answer: B

    Solution :

    (b): \[p(-1)=0\Rightarrow {{\left( -1 \right)}^{4}}+3a(-1)+b=0\] \[\Rightarrow +1-3a+b=0\] \[\Rightarrow -3a+b=1\]                                                      ...,(1) \[p\left( 1 \right)=0\Rightarrow {{1}^{4}}+3a\left( 1 \right)+b=0\Rightarrow 3a+b=-1\]       .....(2) Solving (1) and (2) we get \[3+2b=-1\]           


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