Type the equation that shows the pattern among this set of ordered pairs.
(0, 4), (1, 0), (2, -4), (3, -8)
use slope-intercept form: y = mx + b

Line y=mx+b  has  point (0,b).
If you've got poind (0,4)  -  you can write, that b=4. 
So this is line y=mx+4 
Now slope.  You've got point (1,0), so  for x=1,  y=0.  Substitute:
m * 1 + 4 = 0 
m+4 = 0 
m=-4
So equation of this line is: y=-4x+4