CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2011

  • question_answer
    The length of the latusrectum of \[3{{x}^{2}}-4y+6x-3=0\]is

    A) \[\frac{3}{4}\]                                   

    B) \[\frac{4}{3}\]

    C)  2                                            

    D)  3

    Correct Answer: B

    Solution :

    Given equation of conic \[3{{x}^{2}}-4y+6x-3=0\]                 \[\Rightarrow \]               \[3{{x}^{2}}+6x-3=4y\] \[\Rightarrow \]               \[3({{x}^{2}}+2x-1)=4y\] \[\Rightarrow \]               \[3({{x}^{2}}+2x+1-2)=4y\] \[\Rightarrow \]               \[3{{(x+1)}^{2}}-6=4y\] \[\Rightarrow \]               \[3{{(x+1)}^{2}}=4y+6\] \[\Rightarrow \]               \[{{(x+1)}^{2}}=\frac{4}{3}(y+3/2)\]                        ??(i) Let         \[{{X}^{2}}=\frac{4}{3}Y\]               ...(ii) where \[X=x+1\] and \[Y=y+3/2\] and        \[4b=4/3\Rightarrow \,\,b=1/3\] So, now the length of latuserectum is 4/3.


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