a) A (2, 3), B (2, -4) e C (2, -1)
|
2 3 1
2 −4 1
2 −1 1
|

|
2 3 1
2 −4 1
2 −1 1
| |
2 3
2 −4
2 −1
|

b) A (1, 0), B (-3, 2) e C (2, 4)