Answer:
y = -4/9x
Explanation:
You want the equation of the line through (0, 0) and (9, -4).
Proportion
A line through the point (0, 0) represents a proportion. The slope of the line is the constant of proportionality, the ratio of y to x.
k = y/x = -4/9
The equation of the line is ...
y = kx
y = -4/9x