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7th Class Mathematics Algebraic Expressions Question Bank Algebra

  • question_answer
    The value of \[25{{x}^{2}}+16{{y}^{2}}+40xy\] at \[x=1\] and \[y=-1\]is

    A) 81                               

    B)  \[-49\]

    C) 1                     

    D) None of these

    Correct Answer: C

    Solution :

     \[25{{x}^{2}}+16{{y}^{2}}+40xy\] At\[x=1\]and\[y=-1\] \[25{{(1)}^{2}}+15{{(-1)}^{2}}+40(1)(-1)\] \[=25+16-40=1.\]     


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