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

  • question_answer
    Multiply \[6{{x}^{3}}-y+3{{x}^{2}}y\,\,by\,\,{{x}^{2}}+{{y}^{2}}\]

    A)  \[6{{x}^{5}}-3{{x}^{4}}y-6{{x}^{3}}{{y}^{2}}-6{{x}^{3}}{{y}^{2}}+2{{x}^{2}}{{y}^{3}}-{{y}^{4}}\]

    B)  \[6{{x}^{5}}+3{{x}^{4}}y+6{{x}^{3}}{{y}^{2}}-{{x}^{2}}y+3{{x}^{2}}{{y}^{3}}-{{y}^{3}}\]

    C)  \[6{{x}^{5}}-3{{x}^{4}}y+6{{x}^{3}}{{y}^{2}}+2{{x}^{2}}{{y}^{3}}-{{y}^{5}}\]

    D)  \[6{{x}^{5}}+3{{x}^{4}}y-6{{x}^{3}}{{y}^{2}}+2{{x}^{2}}{{y}^{3}}-{{y}^{5}}\]

    Correct Answer: B

    Solution :

    \[(6{{x}^{3}}-y+3{{x}^{2}}y)\times ({{x}^{2}}+{{y}^{2}})\] \[={{x}^{2}}(6{{x}^{3}}+3{{x}^{2}}y-y)+{{y}^{2}}(6{{x}^{3}}+3{{x}^{2}}y-y)\] \[=6{{x}^{5}}+3{{x}^{4}}y-{{x}^{2}}y+6{{x}^{3}}{{y}^{2}}+3{{x}^{2}}{{y}^{3}}-{{y}^{3}}\]


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