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

  • question_answer
    The function \[f(x)=\frac{{{x}^{2}}}{{{e}^{x}}}\] monotonically increasing if

    A) x < 0 only

    B) x > 2 only

    C) 0 < x < 2

    D) \[x\in (-\infty ,0)\cup (2,\infty )\]

    Correct Answer: C

    Solution :

    [c] \[f(x)=\frac{{{x}^{2}}}{{{e}^{x}}};f'(x)=\frac{2x.{{e}^{x}}-{{e}^{x}}.{{x}^{2}}}{{{\left( {{e}^{x}} \right)}^{2}}}\] \[f'(x)=\frac{2x-{{x}^{2}}}{{{e}^{x}}}\] As \[{{e}^{x}}\] is always positive and for monotonically increasing; \[2x-{{x}^{2}}>0\] \[\Rightarrow {{x}^{2}}-2x<0\Rightarrow x(x-2)<0\Rightarrow x\in (0,2)\]


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