A particle moves along the x-axis its position varies with

Question

Compute the each part of following problem given below:

Problem: A particle moves along the x-axis. Its position varies with time according to the expression x(t) = -6t + 5t², where x is in meters and t is in seconds.

Part I: Determine the displacement of the particle in the two time intervals t = 0 to t = 1 s and t = 1 s to t = 4 s.

Part II: Calculate the average velocity during these two time intervals.

Part III: Find the instantaneous velocity of the particle at t = 2.5 s.

I've been having quite a bit of trouble understanding this problem, Thank You so much for your help.