The correct statement that describes the true relationship between any point on \( f(x) \) and \( -f(x) \) is:
If \( (x,y) \) is on the graph of \( f(x) \), then \( (x,-y) \) is on the graph of \( -f(x) \).
This means that if a point \( (x, y) \) is on the graph of the function \( f(x) \), then the point \( (x, -y) \) will be on the graph of \( -f(x) \), which represents the reflection of \( f \) across the x-axis.