Respostas

2014-03-01T20:47:08-03:00
   \left[\begin{array}{ccc}1&-4&1\\-3&5&1\\4x&3&1\end{array}\right] =0

5 + 16x -9 -20x -3 +12 = 0
-4x +5 = 0
x = 5/4


OBS. Entenda o simbolo [ ] como determinante