To build the function x = x(t), we first need to determine the initial position (X0), initial velocity in the x direction (V0x), and acceleration in the x direction (ax).

Without knowing the values of X0, V0x, and ax, we can still express x in terms of t using the given equation x = 4 + t^2.

Therefore, the function x = x(t) is:

x(t) = 4 + t^2