Explanation:
as the description says, the line is the function f(x).
that means for any value we pick for x the function calculated the corresponding value of y.
and all the fitting pairs of x- and y-values are represented by the line.
we pick an x-value (on the x-axis) and go straight up or down until we hit the line and go horizontally (left or right) to the y-axis and read the y-value there.
f(-2) means that x = -2.
so, we go on the x-axis 2 units left of the origin (0, 0), which is the point, where the x- and y-axis intercept (in the middle of the graph).
2 units left of that point is x = -2.
from there we go down to the line, and from there again right to the y-axis. what do we read there ? -2
so, y = -2.
and that is the same as
f(-2) = -2
FYI : to get y = 2, we have to go even further right than what the graph shows. it looks like y = 2 for x = 6.
so,
f(6) = 2