7th Class Mathematics Algebraic Expressions Question Bank Algebraic Expressions

  • question_answer
    Find the value of \[4xy(x-y)-6{{x}^{2}}(y-{{y}^{2}})-\]\[3{{y}^{2}}(2{{x}^{2}}-x)+2xy(x-y)\] for \[x=5\]and\[y=13\].

    A)  \[-195\]         

    B)  2535              

    C)         \[-2535\]       

    D)         7605

    Correct Answer: C

    Solution :

    We have, \[4xy(x-y)-6{{x}^{2}}(y-{{y}^{2}})\] \[-3{{y}^{2}}(2{{x}^{2}}-x)+2xy(x-y)\] \[=4{{x}^{2}}y-4x{{y}^{2}}-6{{x}^{2}}y+6{{x}^{2}}{{y}^{2}}-6{{x}^{2}}{{y}^{2}}+3x{{y}^{2}}\]\[+2{{x}^{2}}y-2x{{y}^{2}}\] \[=(4{{x}^{2}}y-6{{x}^{2}}y+2{{x}^{2}}y)+(-4x{{y}^{2}}+3x{{y}^{2}}-2x{{y}^{2}})\]\[+(6{{x}^{2}}{{y}^{2}}-6{{x}^{2}}{{y}^{2}})\] \[=0-3x{{y}^{2}}+0=-3(5)\times {{(13)}^{2}}\] \[=-3\times 5\times 169=-2535\]


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