See also Example LEQ.3 for a visual approach to solving a linear equation that parallels the usual algebraic steps.
|For the graph of $f$: Find $y=20$ on the Y axis , then find the point on the graph of $f$ with second coordinate $20$, determine it's first coordinate, $6$, and that is the desired value for $x$.||For the mapping diagram of $f$: Find $y=20$ on the target axis , then find $x$ on the source axis with the function arrow pointing to $20$.|
|To do this, look for the point where the line $y=20$ intersects the line that is the graph of $f$||To do this, find the focus point of
$f$, $F= [5, -10]$ on the mapping diagram. [Use Geogebra?]
Draw the line through F and the point $y=20$, to find the
point of intersection of this line with the X axis, $x=6$,
which is the desired value for $x$.