Questions in pair-st-lines

Select	Question
	If one of the lines given by $6{{x}^{2}}-xy+4c{{y}^{2}}=0$ is $3x+4y=0$, then c equals
	If the sum of the slopes of the lines given by ${{x}^{2}}-2cxy-7{{y}^{2}}=0$ is four times their product, then c has the value
	If $\frac{{{x}^{2}}}{a}+\frac{{{y}^{2}}}{b}+\frac{2xy}{h}=0$ represent pair of straight lines and slope of one line is twice the other. Then $ab:{{h}^{2}}$ is
	If the lines represented by the equation $a{{x}^{2}}-bxy-{{y}^{2}}=0$ make angles $\alpha $ and $\beta $ with the x-axis, then $\tan (\alpha +\beta )$=
	Angle between the lines represented by the equation ${{x}^{2}}+2xy\sec \theta +{{y}^{2}}=0$ is
	If the acute angles between the pairs of lines $3{{x}^{2}}-7xy+4{{y}^{2}}=0$ and $6{{x}^{2}}-5xy+{{y}^{2}}=0$ be ${{\theta }_{1}}$ and ${{\theta }_{2}}$ respectively, then
	The angle between the lines represented by the equation $a{{x}^{2}}+xy+b{{y}^{2}}=0$ will be ${{45}^{o}}$, if
	The lines represented by the equation $9{{x}^{2}}+24xy+16{{y}^{2}}+21x+28y+6=0$ are
	Acute angle between the lines represented by $({{x}^{2}}+{{y}^{2}})\sqrt{3}=4xy$ is
	Angles made by the lines represented by the equation $xy+y=0$with $y-$axis are