Infer primitive curves from a gradient function
Translate gradient signs into the direction and stationary features of a primitive
\[F'(x)=g(x)=-2x+4\]
The functions are defined for all real x. Report open sign intervals split at every zero of g, including a repeated zero. Positive g means F is increasing; negative g means F is decreasing
No function value is supplied, so its vertical translation is undetermined