JCECE Engineering JCECE Engineering Solved Paper-2014

  • question_answer
    For what value\[k\], will the equation \[{{x}^{2}}-(3k-1)x+2{{k}^{2}}+2k=11\]have equal roots?

    A) \[5\]                                     

    B) \[9\]

    C)  Both [a] and [b]              

    D)  \[0\]

    Correct Answer: C

    Solution :

    Given equation is \[{{x}^{2}}-(3k-1)x+2{{k}^{2}}+2k-11=0\] For equal roots                 \[{{b}^{2}}-4ac=0\] \[\Rightarrow \]               \[{{(3k-1)}^{2}}=4(2{{k}^{2}}+2k-11)\] \[\Rightarrow \]               \[9{{k}^{2}}+1-6k=8{{k}^{2}}+8k-44\] \[\Rightarrow \]               \[{{k}^{2}}-14k+45=0\] \[\Rightarrow \]               \[(k-5)(k-9)=0\] \[\Rightarrow \]               \[k=5\] or       \[k=9\]


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