JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    If \[f(x)=\frac{2}{x-3},\ g(x)=\frac{x-3}{x+4}\] and \[h(x)=-\frac{2(2x+1)}{{{x}^{2}}+x-12},\] then \[\underset{x\to 3}{\mathop{\lim }}\,[f(x)+g(x)+h(x)]\] is

    A)                 \[-2\]

    B)                 \[-1\]

    C)                 \[-\frac{2}{7}\]

    D)                 0

    Correct Answer: C

    Solution :

                       We have \[f(x)+g(x)+h(x)=\frac{{{x}^{2}}-4x+17-4x-2}{{{x}^{2}}+x-12}\]            \[=\frac{{{x}^{2}}-8x+15}{{{x}^{2}}+x-12}=\frac{(x-3)\,(x-5)}{(x-3)\,(x+4)}\]                                 \[\therefore \,\,\underset{x\to 3}{\mathop{\lim }}\,\,[f(x)+g(x)+h(x)]=\underset{x\to 3}{\mathop{\lim }}\,\,\,\frac{(x-3)\,\,(x-5)}{(x-3)\,\,(x+4)}=-\frac{2}{7}\].


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