The given linear function is f(x) = x-2
The parent function of this linear equation is y=x
Your friend's way of explaining this function is not quite correct.
If the transformation in the function is of the form
, then the graphs moves up or down vertically in the y- axis direction depending upon the value of c.
If c>0, then the graph moves up.
If c<0, the graph moves down.
Comparing the given equation
with
, we notice, c = -2 which is less than 0.
Hence the graph moves down by 2 units.