J & K CET Engineering J and K - CET Engineering Solved Paper-2009

  • question_answer
    If the equation \[(a+1){{x}^{2}}-(a+2)x+(a+3)=0\] has  roots equal in magnitude but opposite in signs, then the roots of the equation are           

    A)  \[\pm \,\,a\]           

    B)  \[\pm \,\frac{1}{2}\,a\]

    C)  \[\pm \,\frac{3}{2}\,a\]

    D)  \[\pm \,2\,a\]

    Correct Answer: B

    Solution :

    Given equation is \[(a+1){{x}^{2}}-(a+2)x+(a+3)=0\] Since, roots are equal in magnitude and opposite in sign. \[\therefore \]  coefficient of x is zero ie, \[a+2=0\] \[\Rightarrow \] \[a=-2\] ?.(i) \[\therefore \] Equation is \[(-2+1){{x}^{2}}-(-2+2)x+(-2+3)=0\] \[\Rightarrow \] \[-{{x}^{2}}+1=0\] \[\Rightarrow \] \[x=\pm 1\] ?..(ii) Only option [b] ie, \[\pm \frac{1}{2}\] a satisfies Eqs. (i) and (ii).


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