JCECE Engineering JCECE Engineering Solved Paper-2005

  • question_answer
    The focus of the parabola \[{{y}^{2}}-x-2y+2=0\] is:

    A) \[(1/4,\,\,0)\]                   

    B) \[(1,\,\,2)\]

    C) \[(5/4,\,\,1)\]                   

    D) \[(3/4,\,\,5/2)\]

    Correct Answer: C

    Solution :

    Given equation of parabola be                 \[{{y}^{2}}-x-2y+2=0\] \[\Rightarrow \]                      \[{{y}^{2}}-2y+1=x-1\] \[\Rightarrow \]                           \[{{(y-1)}^{2}}=x-1\] \[\Rightarrow \]                                     \[{{Y}^{2}}=X\] where       \[Y=y-1,\,\,X=x-1,\,\,a=\frac{1}{4}\] \[\therefore \]Focus is\[(a,\,\,0)\] \[\Rightarrow \]               \[x-1=\frac{1}{4},\,\,y-1=0\] \[\Rightarrow \]                           \[x=\frac{5}{4},\,\,y=1\] \[\therefore \]  Required focus is\[\left( \frac{5}{4},\,\,1 \right)\].


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