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BCECE Engineering BCECE Engineering Solved Paper-2010

  • question_answer
    The coefficient of x in the quadratic equation \[a{{x}^{2}}+bx+c=0\]was wrongly taken as 17 in place of 13 and its roots were found to be - 2 and - 15, the actual roots of the equation are

    A)  - 2 and 15       

    B)         - 3 and - 10        

    C)         - 4 and- 9           

    D)         -5 and -6

    Correct Answer: B

    Solution :

    The quadratic equation with the roots - 2 and -15 is \[{{x}^{2}}-(-2-15)x+(-2)(-15)=0\] \[\Rightarrow \]               \[{{x}^{2}}+17x+30=0\] Then, according to question, new quadratic equation is                                 \[{{x}^{2}}+13x+30=0\]                 \[\Rightarrow \]               \[(x+3)(x+10)=0\] \[\Rightarrow \]               \[x=-3,-10\] which are the actual required roots.


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