Distance Between Two Parallel Lines

Find the equations of lines parallel to $3x-4y-5=0$ at a unit distance from it.

The distance between the lines $4x+3y=11$ and $8x+6y=15$ is

If the quadrilateral formed by the lines $ax+by+c=0, a^{\text{'}}x+b^{\text{'}}y+c=0,ax+by+c^{\text{'}}=0,a^{\text{'}}x+b^{\text{'}}y+c^{\text{'}}=0$

has perpendicular diagonals, then