Example 1: $m = -2; b = 1: f (x) = -2x + 1$ ![f9x) = -2x + 1](./images/example.LF.2.1.png)
Each arrow passes through a single point, which is labeled $F = [-
2,1]$.
The point $F$ completely determines the function $f$.
Given a point / number, $x$, on the source line,
there is a unique arrow passing through $F$
meeting the target line at a unique point / number, $-2x + 1$, which
corresponds to the linear function's value for the point/number,
$x$.