JEE Main & Advanced Mathematics Definite Integration Question Bank Self Evaluation Test - Application of Integrals

  • question_answer
    The area bounded by the x-axis, the curve \[y=f(x)\] and the lines \[x=1,\text{ }x=b,\] is equal to\[\sqrt{{{b}^{2}}+1}-\sqrt{2}\]  for all \[b>1\], then f(x) is

    A) \[\sqrt{x-1}\]

    B) \[\sqrt{x+1}\]

    C) \[\sqrt{{{x}^{2}}+1}\]

    D) \[\frac{x}{\sqrt{1+{{x}^{2}}}}\]

    Correct Answer: D

    Solution :

    [d] Given \[\int\limits_{1}^{b}{f(x)dx=\sqrt{{{b}^{2}}+1}}-\sqrt{2}\] Differentiate with respect to b \[f(b)=\frac{b}{\sqrt{{{b}^{2}}+1}}\Rightarrow f(x)=\frac{x}{\sqrt{{{x}^{2}}+1}}\]


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