JEE Main & Advanced Mathematics Applications of Derivatives Question Bank Self Evaluation Test - Application of Derivatives

  • question_answer
    The distance of the point on \[y={{x}^{4}}+3{{x}^{2}}+2x\] which is nearest to the line \[y=2x-1\] is

    A) \[\frac{2}{\sqrt{5}}\]

    B)  \[\sqrt{5}\]

    C) \[\frac{1}{\sqrt{5}}\]

    D) \[5\sqrt{5}\]

    Correct Answer: C

    Solution :

    [c] \[y={{x}^{4}}+3{{x}^{2}}+2x\therefore \frac{dy}{dx}=4{{x}^{3}}+6x+2\] Point on curve which is nearest to the line \[y=2x-1\] is the point where tangent to curve is parallel to given line. Therefore, \[4{{x}^{3}}+6x+2=2\] or \[2{{x}^{3}}+3x=0\] or \[x=0,\,\,y=0\]. Therefore, point on the curve at the least distance from the line \[y=2x-1\] is (0, 0). Distance of this point from line is \[\frac{1}{\sqrt{5}}\].


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