Final answer:
The equation y=25x+5 is not directly proportional because it has a y-intercept of 5, which means it does not pass through the origin (0; 0) as directly proportional relationships do.
Step-by-step explanation:
The equation y=25x+5 represents a linear relationship between y and x.
However, for a relationship to be considered directly proportional, the line represented by the equation must pass through the origin (0; 0), meaning it has no y-intercept or the intercept must be zero.
Since this equation has a y-intercept of 5, it is not directly proportional. Direct proportionality is expressed as y = kx, where k is the proportionality constant and there is no y-intercept.
Conversely, inversely proportional relationships have a curve that never cuts the axis and are represented by this format: y = k/x.