Okay, here is my solution:
Particle 1:
a = -4
v0 = 5
x0 = 0
Particle 2:
a = 4
v0 = 0
x0 = 1,28
Therefore;
Particle 1 to the left, particle 2 is on the right:
0 + 5t + 0,5*(-4)t^2 = 1,28 + 0t + 0,5*4t^2
5t - 2t^2 = 2t + 1,28
-4t^2 + 5t - 1,28 = 0
This leaves...