Respostas

2013-07-10T14:57:18-03:00
S = 4 - 8t + 2t²

4 = 4 - 8t + 2t²
- 4 + 4 - 8t + 2t² = 0
-8t + 2t² = 0
t ( -8 + 2t ) = 0
-8 + 2t = 0
2t = 8
t = 8/2
t = 4                   4segundos / 4s

3 4 3