To write the equation of a line in slope-intercept form, we need to use the formula `y = mx + b`, where `m` represents the slope of the line and `b` corresponds to the y-intercept.
Here, we are given that the slope `m` is -2 and the y-intercept `b` is -4.
Now, we just need to plug these values into the formula, replacing `m` with -2 and `b` with -4.
Therefore, plugging in these values gives us the equation:
`y = -2x - 4`
So, the equation of the line with a slope of -2 and a y-intercept of -4 is `y = -2x - 4`. This equation can be used to describe the relationship between the x and y coordinates of any point on this line.