Find an equation for the plane that contains the line x = 1+t, y = 3t, z = 2t and is parallel to the line of intersection of the planes -x+2y+z = 0 and x + z + 1 = 0. On the attachment, the answer is there. My question is, (on the first page) right after he wrote, x,y, leading, z free, he wrote down the matrix form of the equation. Where did he get the values of the matrix right after z. The values are -1, -1 and 1. How did he find them, or where did he get them? Please explain, thanks!