Visualizing Addition and Subtraction of Negative Numbers on a Number Line

① This example demonstrates how to add and subtract negative numbers using a dynamic number line, making the abstract rules of signed-number arithmetic visually concrete. ② Core mathematical concepts include integer addition and subtraction, the number line, opposite numbers, and the sign rules, especially that subtracting a negative is equivalent to adding its positive counterpart. ③ Construction highlights: The GeoGebra commands CircleArc, Line, Mirror, Arc, and Sequence are used to build the number line and its tick marks; objects such as A, intervalsize, one, two, B, C, D, E control the step size and point positions; text1–text5 display the operation and result; list1 and list2 manage sequences for dynamic updates)Skip. ④ This is suitable for middle school students (Grade 7) learning rational number operations, as well as for teachers demonstrating the concept in class. By dragging sliders or selecting points, learners can observe how arrows change direction and length, reinforcing the meaning of adding or subtracting negative numbers.