CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2004

  • question_answer
    If \[a{{x}^{2}}-{{y}^{2}}+4x-y=0\] represents a pair of lines, then a is equal to :

    A)  - 16                                       

    B)  16

    C)  4                                            

    D)  - 4

    Correct Answer: B

    Solution :

    We have, \[a{{x}^{2}}-{{y}^{2}}+4x-y=0\] Here, \[a=a,\,h=0,\,b=-1;\,f=-\frac{1}{2},\,g=2,\,c=0\] for the straight lines \[\left| \begin{matrix}    a & h & g  \\    h & b & f  \\    g & f & c  \\ \end{matrix} \right|=0\] \[\Rightarrow \left| \begin{matrix}    a & 0 & 2  \\    0 & -1 & -1/2  \\    2 & 1/2 & 0  \\ \end{matrix} \right|=0\] \[\Rightarrow \,a\left[ 0+\left( -\frac{1}{4} \right) \right]-0+2\,[2]=0\] \[\Rightarrow \]               \[-\frac{a}{4}+4=0\] or                            \[a=16\]


You need to login to perform this action.
You will be redirected in 3 sec spinner