JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    If\[y=\frac{1}{{{t}^{2}}-t-6}\]and\[t=\frac{1}{x-2}\], then the values of \[x\]which make the function \[y\] discontinuous, are

    A) \[2,\,\,\frac{2}{3},\,\,\frac{7}{3}\]

    B) \[2,\,\,\frac{3}{2},\,\,\frac{7}{3}\]

    C) \[2,\,\,\frac{3}{2},\,\,\frac{3}{7}\]

    D)  None of the above

    Correct Answer: B

    Solution :

    Clearly; the function\[t=\frac{1}{x-2}\]is discontinuous at \[x=2\] and the function\[y=\frac{1}{{{t}^{2}}-t-6}\]is discontinuous at the points, where                 \[{{t}^{2}}-t-6=0\] \[\Rightarrow \]               \[(t+2)(t-3)=0\] \[\Rightarrow \]               \[t=-2,\,\,3\] But         \[t=-2\] \[\Rightarrow \]               \[\frac{1}{x-2}=-2\] \[\Rightarrow \]               \[x-2=-\frac{1}{2}\] \[\Rightarrow \]               \[x=\frac{3}{2}\] and        \[t=3\] \[\Rightarrow \]               \[\frac{1}{x-2}=3\] \[\Rightarrow \]               \[x-2=\frac{1}{3}\] \[\Rightarrow \]               \[x=\frac{7}{3}\] Therefore, the values of \[x\] which make the function \[y\] discontinuous are\[x=2,\,\,\,\frac{3}{2}\]and\[\frac{7}{3}\].


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