David S. answered 11/24/19
Experienced AP Chemistry/Physics Teacher (HS thru College)
Basically, you just want to consider both functions independently.
Looking at the first one, x-4 for values less than 2 is just a straight line with positive one slope passing through the y-axis at -4. Notice that this line arrives at (2, -2), but does not include it.
Then, for x = 2 and greater, we have a straight line with a negative two slope that would have passed through the y-axis at positive two (but x=0 is not included in this function). Notice that this line originates at (2, -2) and does include it.