Question

Find direction numbers for the line of intersection of the planes x + y + z = 7 and x + z = 0. (enter your answers as a comma-separated list.)

Answer 1

The line of intersection has a direction vector that is the cross product of the normal vectors of the given planes.

... [1, 1, 1] × [1, 0, 1] = [1, 0, -1] . . . . . . using a suitable calculator

The direction numbers of the line of intersection are (1, 0, -1).