8th Class Mathematics Algebraic Expressions Question Bank Algebraic Expressions and Identities

  • question_answer
    What must be subtracted from \[{{x}^{4}}+2{{x}^{2}}-3x+7\] to get \[{{x}^{3}}+{{x}^{2}}+x-1?\]

    A)  \[{{x}^{4}}-{{x}^{3}}+{{x}^{2}}-4x+8\]

    B)  \[{{x}^{3}}+{{x}^{2}}-4x+8\]

    C)  \[{{x}^{4}}-{{x}^{3}}+{{x}^{2}}+4x-8\]

    D)  \[{{x}^{4}}-{{x}^{3}}-{{x}^{2}}+4x-8\]

    Correct Answer: A

    Solution :

    Required expression \[=({{x}^{4}}+2{{x}^{2}}-3x+7)-({{x}^{3}}+{{x}^{2}}+x-1)\] \[={{x}^{4}}+2{{x}^{2}}-3x+7-{{x}^{3}}-{{x}^{2}}-x+1\] \[={{x}^{4}}-{{x}^{3}}+2{{x}^{2}}-{{x}^{2}}-3x-x+7+1\] \[={{x}^{4}}+\frac{1}{4}{{x}^{3}}-\frac{3}{2}{{x}^{2}}+\frac{3}{4}x\]


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