The equation of the line in the graph is y= x+

y = -x - 1

Step-by-step explanation:

The line heads downward as x increases, meaning that y decreases.  For each unit increase in x, y decreases by 1, so the slope of this line is

m = rise/run = -1/1, or just -1.  The y-intercept is readily identified:  it is (0, -1).

Thus, the equation of this line is   y = -x - 1