`frac {x-b}{a}=\frac {y-1}{1}=\frac {z-d}{c}`

`frac {x-b-a}{a}=\frac {y-1}{1}=\frac {z-d-c}{c}`

`frac {x-a}{b}=\frac {y-0}{1}=\frac {z-c}{d}`

`frac {x-b-a}{b}=\frac {y-1}{0}=\frac {z-d-c}{d}`