JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2009

  • question_answer
        The equation of the tangent to the curve \[y=(2x-1){{e}^{2(1-x)}}\]at the points its maximum, is

    A)  \[y-1=0\]                           

    B)  \[x-1=0\]

    C)  \[x+y-1=0\]                      

    D)  \[x-y+1=0\]

    Correct Answer: A

    Solution :

                    \[y=(2x-1){{e}^{2(1-x)}}\] \[\Rightarrow \]               \[\frac{dy}{dx}=2{{e}^{2(1-x)}}-2(2x-1){{e}^{2(1-x)}}\]                 \[=2{{e}^{2(1-x)}}(2-2x)\]                 \[=4{{e}^{2(1-x)}}(1-x)\] Put,        \[\frac{dy}{dx}=0\Rightarrow x=1\] Now, \[\frac{{{d}^{2}}y}{d{{x}^{2}}}=-8{{e}^{2(1-x)}}(1-x)-4{{e}^{2(1-x)}}\] \[\Rightarrow \]               \[{{\left( \frac{{{d}^{2}}y}{d{{x}^{2}}} \right)}_{x=1}}=-4<0\] So, y is maximum at\[x=1,\]when\[x=1,\text{ }y=1\] Thus, the point of maximum is (1,1). The equation of the tangent at (1,1) is                 \[y-1=0(x-1)\]or \[y=1\]


You need to login to perform this action.
You will be redirected in 3 sec spinner