The y intercept is at -2 = (0, - 2)

The slope of the line from this point moving to the right is [ change in y / change in x ] = [2 units / 4 units] = 2/4 = 1/2

So....the equation is y = mx + b where m is the slope and b is the y intercept

So..we have

y = (1/2)x - 2