┌──────────┐
                                                  │ 2
x = -3a + 2b + 3c - d ╮                      -y ±⟍│y  - 4 x z
y =    3a - b - 3c    ╞  C(t) = 0   ==>  t = ─────────────────
z =       c - a       ╯                             2x