In space, a straight line can be regarded as the intersection of two planes.

Suppose a known plane?

Because the point at the intersection of two planes must satisfy two equations, we can get?

This system of equations is called. General equation of space straight line.

There are infinitely many planes passing through the spatial straight line L. As long as two planes are randomly selected from these infinite planes and their equations are combined, the equation obtained represents the spatial straight line l .- From Tongji Edition Advanced Mathematics.