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9th Class Mathematics Polynomials Question Bank Polynomials

  • question_answer
    If \[\mathbf{x}=\mathbf{2},\] \[\mathbf{y}=\mathbf{3}\] and \[\mathbf{z}=-\mathbf{5},\] then \[{{\mathbf{x}}^{\mathbf{3}}}\mathbf{+}{{\mathbf{y}}^{\mathbf{3}}}\mathbf{+}{{\mathbf{z}}^{\mathbf{3}}}\mathbf{=}\]

    A)  90                               

    B)  -90         

    C)  0                                

    D)  368

    Correct Answer: B

    Solution :

    (b): \[x+y+z=2+3-5=0\] \[\therefore x+y+z=0~\,\,\,\therefore {{x}^{3}}+{{y}^{3}}+{{z}^{3}}=3xyz\] \[=3\times 2\times 3\times \left( -5 \right)=-90\] 


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