BCECE Engineering BCECE Engineering Solved Paper-2010

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

    A)  \[\left( \frac{1}{4},0 \right)\]    

    B)         \[(1,2)\]             

    C)         \[\left( \frac{5}{4},1 \right)\]    

    D)         \[\left( \frac{3}{4},\frac{5}{2} \right)\]

    Correct Answer: C

    Solution :

    We have the equation of parabola \[{{y}^{2}}-x-2y+2=0\]                 \[\Rightarrow \]               \[{{y}^{2}}-2y+1=x-1\]                 \[\Rightarrow \]               \[{{(y-1)}^{2}}=x-1\]                 \[\Rightarrow \]               \[{{Y}^{2}}=X\]                 \[\Rightarrow \]               \[{{Y}^{2}}=4.\left( \frac{1}{4}X \right),\] where \[Y=y-1\]and \[X=x-1\] Its focus is given by \[(a,0)=\left( \frac{1}{4},0 \right)\]                 ie,           \[X=\frac{1}{4}\Rightarrow x-1=\frac{1}{4}\]                 \[\Rightarrow \]               \[x=\frac{5}{4}\]                 and        \[Y=0\]                 \[\Rightarrow \]               \[y-1=0\]                 \[\Rightarrow \]               \[y=1\] Hence, focus of given hyperbola is\[\left( \frac{5}{4},1 \right)\]


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