Exercise 68

Which of the following four lines are parallel? Are any of them identical? \(L_1: x = 1 + 6t, y = 1 - 3t, z = 12t + 5\) \(L_2: x = 1 + 2t, y = t, z = 1 + 4t\) \(L_3: 2x - 2 = 4 - 4y = z + 1\) \(L_4: \mathbf{r} = \langle 3, 1, 5 \rangle + t\langle 4, 2, 8 \rangle\)