JEE Main & Advanced Mathematics Functions Question Bank Continuity

  • question_answer
    Let \[f(x)=\left\{ \begin{align}   & \frac{{{x}^{3}}+{{x}^{2}}-16x+20}{{{(x-2)}^{2}}},\text{if}\ x\ne 2 \\  & \ \ \ \ \ \,\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \,\ k,\ \text{if}\ x=2 \\ \end{align} \right.\].  If \[f(x)\] be continuous for all x, then k =                                        [IIT 1981]

    A)            7

    B)            ?7

    C)            \[\pm 7\]

    D)            None of these

    Correct Answer: A

    Solution :

               For continuous \[\underset{x\to 2}{\mathop{\lim }}\,\,f(x)=f(2)=k\]                    \[\Rightarrow \,\,k=\underset{x\to 2}{\mathop{\lim }}\,\frac{{{x}^{3}}+{{x}^{2}}-16x+20}{{{(x-2)}^{2}}}\]            \[=\underset{x\to 2}{\mathop{\lim }}\,\,\frac{({{x}^{2}}-4x+4)\,\,(x+5)}{{{(x-2)}^{2}}}=7\] .


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