Respostas

2014-03-13T22:15:28-03:00
  \left[\begin{array}{ccc}-1&2\\2&4\\x&y\\-1&2\end{array}\right]

Ou seja, temos:

4 + 4x + (-y) - (-4) - (+2y) - (+2x) = 0
4 + 4x - y + 4 - 2y - 2x = 0
- 3y + 2x + 8 = 0