Answer:
It's a kinematic equation.
Step-by-step explanation:
x displacement = (velocity_final * time) - (0.5 * acceleration * time * time)
You should be given a value, context(word problem), or diagram.
If you're deriving for a term just isolate the term.
If you're asking why the -(0.5 * acceleration * time * time) is negative instead of positive, would need context.