As per the question the particle moves along X-axis.
The position of the particle is a function of time
As per the question the position [tex]x=6.8t+8.5t^2[/tex]
The velocity of the particle is given as [tex]v=\frac{dx}{dt}[/tex]
v=6.8+17t
The acceleration of the particle is given as
[tex]a=\frac{dv}{dt}[/tex]
a=17
Here the acceleration is a constant quantity which is independent of time.
From the acceleration obtained here one can infer that particle is moving with uniform acceleration .