a)
E: X = [1, 1, -1] + r·([3, 5, 1] - [1, 1, -1]) + s·([5, 5, 7] - [1, 1, -1])
E: X = [1, 1, -1] + r·[2, 4, 2] + s·[4, 4, 8]
b)
[1, 1, -1] + r·[2, 4, 2] + s·[4, 4, 8] = [-1, 0, -6] --> r = 0.5 ∧ s = -0.75
Damit liegt D in der Ebene ABC.
c)
[1, 1, -1] + r·[2, 4, 2] + s·[4, 4, 8] = [5, 6, 6] --> r = 0.5 ∧ s = 0.75
r + s > 1 → Damit liegt F nicht im Dreieck.