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

  • question_answer
    The equation of the tangent to the curve \[y={{e}^{-\left| x \right|}}\]at the point where the curve cuts the line \[x=1\] is

    A) \[e(x+y)=1\]

    B) \[y+ex=1\]

    C) \[y+x=e\]

    D) None of these

    Correct Answer: D

    Solution :

    [d] We have equation of tangent to any curve f(x) at \[({{x}_{1}},\,\,{{y}_{1}})\] is \[(y-{{y}_{1}})={{\left. \frac{dy}{dx} \right|}_{({{x}_{1}},{{y}_{1}})}}(x-{{x}_{1}})\] Given curve is \[y={{e}^{-\left| x \right|}}\] Point of intersection is \[\left( 1,\,\,\frac{1}{e} \right)\,\,at\,\,x=1,\,\,\left| x \right|=x\] So, \[y={{e}^{-x}}\Rightarrow \frac{dy}{dx}=-{{e}^{-x}}\therefore {{\left( \frac{dy}{dx} \right)}_{x=1}}=-{{e}^{-1}}\] Therefore, equation of tangent is \[y-\frac{1}{e}=\frac{-1}{e}(x-1)\Rightarrow x+ey=2\]


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