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The applet below illustrates horizontal stretching and compression. The red graph is f(x), and the green graph is f(ax). Use the slider to explore the effect of changing the vertical shift by changing the value of a.
Note that a>1 is a compression, and a<1 is a stretch.
Also, when a is negative, then the stretching is combined with a horizontal reflection. For example, when a=-1, the green graph is the reflection of the red graph in the y-axis.
Experiment further by entering your own function
for f(x) (remember to change the second function accordingly).
MultiGraph applet written by David Eck (http://math.hws.edu/javamath/index.html)
Math 30 home page