Geometric Explanation of the Sign of a Product of Two Numbers

This example demonstrates the geometric interpretation of the sign of the product of two numbers using dynamic geometry. Key math concepts include number line, product sign, and geometric representation. GeoGebra commands like Line and Intersect are used to draw axes and find intersections, with text objects labeling points such as a_1, c_1, A, C, B. Suitable for middle school students and above to understand the connection between product signs and geometric meanings, or for calculus instruction on function sign changes.