The straight lines represented by the equation $9 x^{2}-12 x y+4 y^{2}=0$ are
The straight lines represented by the equation $9 x^{2}-12 x y+4 y^{2}=0$ are
coincident
perpendicular
intersect at $60^{\circ}$
parallel
Solution
The given pair of lines are of the form $a x^{2}+2 h x y+b y^{2}=0 \Rightarrow a=9,2 h=-12, \Rightarrow h=-6, b=4$ $h^{2}-a b=(-6)^{2}-(9 \times 4)=36-36=0$
Therefore the lines are coincident