Function defined on the set of real numbers by a relationship of the form y = kx + b where k and b are non-zero real numbers.
The graph of a partial variation function does not pass through the origin (0,0) of the Cartesian plane, since b ≠ 0.
Example
This is the graph of the function f defined by the rule f(x) = 3x − 4.
The rate of change of this function is 3.