Absolute value graphs are shaped like a "V" where x = h is the bottom of the "V" when y=|x-h|.
So lets use x=4, 5, and 6. For each x value wee will plug it into the equation to get a y value. If the function were linear, the y values should change at a constant rate in the same direction (slope).
f(4) = 1
f(5) = 0
f(6) = 1
As you can see, the function is not linear because it goes from decreasing to increasing.
