You can use matrices and row elimination, or (equivalently) solve simultaneously.[br]Using the normals, consider whether any planes are parallel or coincident to determine the number of possible solutions for the system of equations.

- Cross product of the two normals will give the direction vector of the intersecting line, then find a common point on both planes.[br]- Attempt to solve simultaneously (I prefer Gaussian Elimination), and construct a vector equation from there.[br]- LinSolve in GDC will give the equation of the line.

You can use matrices and row elimination, or (equivalently) solve simultaneously.[br]Using the normals, consider whether any planes are parallel or coincident to determine the number of possible solutions for the system of equations.

- Cross product of the two normals will give the direction vector of the intersecting line, then find a common point on both planes.[br]- Attempt to solve simultaneously (I prefer Gaussian Elimination), and construct a vector equation from there.[br]- LinSolve in GDC will give the equation of the line.

All the lines are parallel, and they go in the direction of the cross product of the normals of each of the planes.