JEE Main & Advanced Mathematics Pair of Straight Lines Question Bank Equation of Pair of Straight Lines

  • question_answer
    The equation \[{{(x-5)}^{2}}+(x-5)\,(y-6)\,-2\,{{(y-6)}^{2}}=0\] represents

    A)            A circle

    B)            Two straight lines passing through origin

    C)            Two straight lines passing through the point (5, 6)

    D)            None of these

    Correct Answer: C

    Solution :

               \[{{(x-5)}^{2}}+(x-5)(y-6)-2{{(y-6)}^{2}}=0\]                    Þ \[{{x}^{2}}+25-10x+xy+30-6x-5y-2{{y}^{2}}-72+24y=0\]                    \[\Rightarrow {{x}^{2}}+xy-2{{y}^{2}}-16x+19y-17=0\]                    Obviously, it is not a circle as \[a\ne b\]and xy is present. On checking for pair of straight lines, we get that the equation represents a pair of straight lines.                    Also for \[x=5,\ y=6,\]equation vanishes. Therefore it passes through (5, 6).


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