JEE Main & Advanced JEE Main Paper (Held On 26 May 2012)

  • question_answer
    If\[a,b,c\in R\] and 1 is a root of equation \[a{{x}^{2}}+bx+c=0,\]then the curve \[y=4a{{x}^{2}}+3bx+2c,a\ne 0\]intersect x-axis at.   JEE Main Online Paper (Held On 26-May-2012)  

    A) two distinct points whose coordinates are always rational numbers

    B)        no point

    C)                        exactly two distinct points

    D)                        exactly one point

    Correct Answer: D

    Solution :

                    Given \[a{{x}^{2}}+bx=c=0\]\[\Rightarrow \]\[a{{x}^{2}}=-bx-c\] \[y=4a{{x}^{2}}+3bx+2c\] \[=4[-bx-c]+3bx+2c\] \[=-4bx-4c+3bx+2c\] \[=-bx-2c\] Since, this curve intersects x-axis . \[\therefore \]put y = 0, we get\[-bx-2c=0\Rightarrow -bx=2c\]\[\Rightarrow \]\[x=\frac{-2c}{b}\] Thus, given curve intersects x-axis at exactly one point.


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