Questions in pair-st-lines

Select	Question
	The condition of representing the coincident lines by the general quadratic equation $f(x,\,y)=0$, is
	The equation ${{x}^{2}}+k{{y}^{2}}+4xy=0$represents two coincident lines, if $k =$
	The joint equation of the straight lines $x+y=1$and $x-y=4$is
	The value of $\lambda $ for which the equation ${{x}^{2}}-\lambda xy+2{{y}^{2}}+3x-5y+2=0$ may represent a pair of straight lines is
	$2{{x}^{2}}+7xy+3{{y}^{2}}+8x+14y+\lambda =0$ will represent a pair of straight lines, when $\lambda $=
	The gradient of one of the lines ${{x}^{2}}+hxy+2{{y}^{2}}=0$ is twice that of the other, then $h =$
	If the point (2,–3) lies on $k{{x}^{2}}-3{{y}^{2}}+2x+y-2=0$, then $k$ is equal to
	If $L{{x}^{2}}-10xy+12{{y}^{2}}$$+5x-16y-3=0$ represents a pair of straight lines, then $L$ is
	If the ratio of gradients of the lines represented by $a{{x}^{2}}+2hxy+b{{y}^{2}}=0$is 1 : 3, then the value of the ratio ${{h}^{2}}:ab$is
	If the slope of one line of the pair of lines represented by $a{{x}^{2}}+4xy+{{y}^{2}}=0$is 3 times the slope of the other line, then a is