10th Class Mathematics Quadratic Equations Question Bank Quadratic Equations

  • question_answer
    If one of roots of \[2{{x}^{2}}+ax+32=0\] is twice the other root, then the value of a is _____?

    A)  \[-3\sqrt{2}\]        

    B)  \[8\sqrt{2}\]   

    C)         \[12\sqrt{2}\]         

    D)                     \[-2\sqrt{2}\]  

    Correct Answer: C

    Solution :

    Equation is \[2{{x}^{2}}+ax+32=0\] Let one root be \[\alpha ,\] then other would be\[2\alpha .\] Now,  \[\alpha \times 2\alpha =16\] \[\Rightarrow \] \[\alpha =\pm \,2\sqrt{2}\] and \[\alpha +2\alpha =-a/2\] \[\Rightarrow \] \[3\alpha =-a/2\] \[\Rightarrow \] \[6\alpha =-a\] \[\Rightarrow \]     \[\pm \,12\sqrt{2}=-a\]  or  \[a=\pm 12\sqrt{2}\]


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