For the graph of $f$: Find $x=8$ on the X axis, then find the point on the graph of $f$ directly above (below) that point, $(8,2)$, determine it's second coordinate, $2$, and that is the desired value for $y$. | For the mapping diagram of $f$: Find $x=8$ on the X axis, then find the focus point of $f$, $F= [\frac 1 2, -2]$ on the mapping diagram. Draw the line through F and the point $x=8$, to find the point of intersection of this line with the Y axis, $y=2$, which is the desired value for $y$. |