JEE Main & Advanced JEE Main Paper (Held On 11 April 2014)

  • question_answer
    If\[\underset{x\to 2}{\mathop{\lim }}\,\frac{\tan \left( x-2 \right)\left\{ {{x}^{2}}+\left( k-2 \right)x-2k \right\}}{{{x}^{2}}-4x+4}=5,\]then k is equal to:   [JEE Main Online Paper ( Held On 11 Apirl  2014 )

    A) 0                                             

    B) 1

    C) 2                                             

    D) 3

    Correct Answer: D

    Solution :

                    \[\underset{x\to 2}{\mathop{\lim }}\,\frac{\tan (x-2)\{{{x}^{2}}+(k-2)x-2k\}}{{{x}^{2}}-4x+4}=5\] \[\Rightarrow \]\[\underset{x\to 2}{\mathop{\lim }}\,\frac{\tan (x-2)\{{{x}^{2}}+kx-2x-2k\}}{{{(x-2)}^{2}}}=5\] \[\Rightarrow \]\[\underset{x\to 2}{\mathop{\lim }}\,\frac{\tan (x-2)\{x(x-2)+k(x-2)\}}{(x-2)\times (x-2)}=5\] \[\Rightarrow \]\[\underset{x\to 2}{\mathop{\lim }}\,\left( \frac{\tan (x-2)}{(x-2)} \right)\times \underset{x\to 2}{\mathop{\lim }}\,\left( \frac{(k+2)\cancel{(x-2)}}{\cancel{(x-2)}} \right)=5\] \[\Rightarrow \]\[1\times \underset{x\to 2}{\mathop{\lim }}\,(k+x)=5\]               \[\left\{ \because \underset{h\to 0}{\mathop{\lim }}\,\frac{\tanh }{h}=1 \right\}\]or\[k+2=5\]\[\Rightarrow \]\[\]


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