If the lines $ax + 2y + 1 = 0$,$bx + 3y + 1 = 0$,and $cx + 4y + 1 = 0$ are concurrent,then $a, b, c$ are in:

The lines $x-y-2=0$,$x+y-4=0$,and $x+3y=6$ meet at a common point:

If the lines $L_1 \equiv 2x + y + 3 = 0$,$L_2 \equiv kx + 2y - 3 = 0$,and $L_3 \equiv 3x - 2y + 1 = 0$ are concurrent,then the cosine of the acute angle between the lines $L_2 = 0$ and $2x - 5y + 7 = 0$ is

At which point are the lines $ax + by + c = 0$ and $3a + 2b + 4c = 0$ concurrent?

The lines $x-2y+1=0$,$2x-3y-1=0$,and $3x-y+k=0$ are concurrent. The angle between the lines $3x-y+k=0$ and $mx-3y+6=0$ is $45^{\circ}$. If $m$ is an integer,then $m-k=$

If three non-zero real numbers $a, b, c$ are in harmonic progression,then the straight lines $\frac{x}{a} + \frac{y}{b} - \frac{2}{c} = 0$ are concurrent at the point