Question

Find the projection of the line 3x – y +2z – 1 = 0, x +2y – z = 2 on the plane 3x + 2y +z = 0.

Answer 1

All three equations you've given correspond to planes. Which 'line' is supposed to be considered?

Answer 2

probably the intersection of the first two planes.

Answer 3

Find the projection of the line 3x – y +2z – 1 = 0, x +2y – z = 2 on the plane 3x + 2y +z = 0