Explanation:
Pick any two negative numbers to represent the x and y intercepts. Let's say we go for -2 and -3 as the x and y intercepts.
That leads to the locations (-2,0) and (0,-3)
Find the slope through these two points.
m = (y2-y1)/(x2-x1)
m = (-3-0)/(0-(-2))
m = (-3-0)/(0+2)
m = -3/2
m = -1.5
We get a negative slope. The line moves downhill as we move to the right.