Question

write the equation of x displacement and y displacement of an object moving in a plane with acceleration ​

Answer 1

The 4t and 5t can be combined into 9t, and this is your initial velocity (or change in x over change in t) term, so the velocity starts at +9. The 3 is your initial position term so the object starts at a position +3. x is you position at any time t. Since there is no t^2 term there is no change in velocity (or 2nd derivative) term, so the acceleration is 0 and the velocity is constant over all values of t. At t=3 the acceleration is 0, velocity is 9, and your position is 30.