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Henri Picciotto's Math Education Page
You can move the ○s.
This applet is best used after making many rectangles with the Lab Gear blocks. Use it as a way to trigger discussion of patterns. What is the relationship between the numbers in the factored form and the ones in the expanded form? How do you see that relationship visually in the image?
The applet can also be used by teachers and students to create images for copying and pasting into a word processing or other document.