10th Class Mathematics Related to Competitive Exam Question Bank Algebra

  • question_answer
    \[f(x),g(x)\] are two polynomial with integer coefficient such that their HCF is 1 and LCM is \[({{x}^{2}}-4)({{x}^{4}}-1)\]lf \[f(x)={{x}^{3}}-2{{x}^{2}}-x+2\] then \[g(x)\]is

    A)  \[{{x}^{3}}-2{{x}^{2}}+x+2\]

    B) \[{{x}^{3}}-2{{x}^{2}}+x-2\]

    C)  \[{{x}^{3}}+2{{x}^{2}}+x+2\]  

    D)  \[{{x}^{3}}-2{{x}^{2}}-x-2\]

    Correct Answer: C

    Solution :

                    Product of the polynomials                 \[=\]Product of their \[LCM\] and\[HCF\] \[\therefore \]  \[f(x).g(x)=LCM\times HCF\] or            \[g(x)=\frac{1\cdot ({{x}^{2}}-4)({{x}^{4}}-1)}{{{x}^{3}}-2{{x}^{2}}-x+2}\]                 \[=\frac{(x-2)(x+2)(x-1)(x+1)({{x}^{2}}+1)}{{{x}^{2}}(x-2)-(x-2)}\]                 \[=(x+2)({{x}^{2}}+1)\]                 \[={{x}^{3}}+2{{x}^{2}}+x+2\]


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