m: (-1, 2, 1)
L = Line((0, 0, 0), Vector[(x(m), y(m), z(m))])
p: x + y - z = 1
q: (2 * x) + y = 2
s = 3.6 (slider from -3 to 4, step 0.01)
v: (1, 0, 0) + (s * m)