J & K CET Engineering J and K - CET Engineering Solved Paper-2014

  • question_answer
    Find the range of the function \[f:[0,\,1]\to R,\,\,f(x)={{x}^{3}}-{{x}^{2}}+4x+2{{\sin }^{-1}}x\]?

    A)  \[[-(\pi +2),\,0]\]

    B)  \[[0,4+\pi ]\]

    C)  \[[2,3]\]

    D)  \[(0,\,2+\pi ]\]

    Correct Answer: B

    Solution :

    We have \[f:[0,\,1]\to R\] \[f(x)={{x}^{3}}-{{x}^{2}}+4x+2{{\sin }^{-1}}x\] Now \[f'(x)=3{{x}^{2}}-2x+4+\frac{2}{\sqrt{1-{{x}^{2}}}}\] For \[x\,[0,\,\,1],\,\,\,f'\,(x)>0\] Hence, it is a increasing function at \[x=0,\,f(0)=0-0+4(0)+2si{{n}^{-1}}(0)=0\] at \[x=1,f(1)=1-1+4(1)+2{{\sin }^{-1}}(1)\] \[=4+2\left( \frac{\pi }{2} \right)=4+\pi \] \[\therefore \]   Range of \[f(x)\,[0,\,4+\pi ]\]


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