Questions in pair-st-lines

Select	Question
	If in general quadratic equation $f(x,y)=0,\Delta =0$ and $a+b=0$, then the equation represents
	The angle between the lines represented by the equation ${{x}^{2}}-2pxy+{{y}^{2}}=0$, is
	The angle between the lines represented by the equation $a{{x}^{2}}+2hxy+b{{y}^{2}}=0$is given by
	The equation ${{x}^{2}}+{{k}_{1}}{{y}^{2}}+{{k}_{2}}xy=0$ represents a pair of perpendicular lines, if
	The angle between the pair of lines $2{{x}^{2}}+5xy+2{{y}^{2}}+3x+3y+1=0$ is
	The straight lines represented by the equation $9{{x}^{2}}-12xy+4{{y}^{2}}=0$ are
	The angle between the two straight lines $2{{x}^{2}}-5xy+2{{y}^{2}}-3x+3y+1=0$ is
	The acute angle formed between the lines joining the origin to the points of intersection of the curves ${{x}^{2}}+{{y}^{2}}-2x-1=0$ and $x+y=1$, is
	The angle between the lines given by ${{x}^{2}}-{{y}^{2}}=0$ is
	Condition that the two lines represented by the equation $a{{x}^{2}}+2hxy+b{{y}^{2}}=0$to be perpendicular is