The problem states that the distance travelled (d) is directly proportional to the square of time (t^2), therefore we can write this in the form of:
d = k t^2
where k is the constant of proportionality in furlongs / s^2
Using the 1st condition where d = 2 furlongs, t = 2 s, we calculate for the value of k:
2 = k (2)^2
k = 2 / 4
k = 0.5 furlongs / s^2
The equation becomes:
d = 0.5 t^2
Now solving for d when t = 4:
d = 0.5 (4)^2
d = 0.5 * 16
d = 8 furlongs
It traveled 8 furlongs for the first 4.0 seconds.