| -3a - 4 + 1 | / √(a² + 1) = | 6a + 3 + 1 | / √(a² + 1)
| 3a + 3 | = | 6a + 4 |
3a + 3 = 6a + 4 或 3a + 3 + 6a + 4 = 0
a = -1/3 或 a = -7/9