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9th Class Mathematics Polynomials Question Bank Polynomials

  • question_answer
    If \[\mathbf{a}+\mathbf{b}+\mathbf{c}=\mathbf{12}\]and a2 + b2 + c2 = 50, then the value of \[\mathbf{ab}+\mathbf{be}+\mathbf{ca},\]is

    A)  44                               

    B)  22             

    C)  23                               

    D)  47

    Correct Answer: D

    Solution :

    (d) \[{{\left( a+b+c \right)}^{2}}={{a}^{2}}+{{b}^{2}}+{{c}^{2}}+2\left( ab+bc+ca \right)\] \[144=50+2\left( ab+bc+ca \right)\] \[\therefore ab+bc+ca=\frac{94}{2}=47\]


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