# Plane Equations

## Main Question or Discussion Point

According to my book, if we write the equation of a plane as:

$ax + by + cz = d$

And two planes have values of $d$ with the same sign, they are on the same side of the origin. If they have values of $d$ with different signs, they are on opposite sides of the origin.

I'm confused as to whether this applies strictly to two parallel planes, or any pair of planes.

jbriggs444
Homework Helper
2019 Award
You must decide what "same side of the origin" means for non-parallel planes.

You must decide what "same side of the origin" means for non-parallel planes.
What about parallel planes? If both sides of the plane equation (cartesian form) are multiplied by -1, the position of the plane is unaltered, right?

jbriggs444