Answer: It moves the function 'a' units up if a > 0. Or it moves the function |a| units down if a < 0.
Step-by-step explanation:
Consider an example like y = f(x)+2. This shifts the f(x) curve 2 units up because we're adding 2 to each y or f(x) output. A point like (5,7) shifts up to (5,9).
As another example, y = f(x)-5 moves the curve 5 units down.
In the first example, we had a > 0 which moved the function 'a' units up (a = 2 in that case). The second example had a = -5 which means a < 0, so that's why we shifted |a| = |-5| = 5 units down.