Equations of Constant Acceleration

When do the 3 equations of constant acceleration apply?
Constant acceleration= velocity changes linearly in velocity time graph, position changes non-linearly in speed time graph
What does Newtowns Law of Gravitation state?
Acceleration due to gravity is constant for all objects despite size i.e. -9.8ms^-2
What does Newtowns Law of Gravitation mean for solving constant acceleration problems?
We always have acceleration(gravity) acting in the y axis
How do you decide which equation to use?
The easiest one with only 1 unknown
Do we solve with both axis in constant acceleration?
No only one axis