Signed Integer Addition and Subtraction on a Number Line

This example visually demonstrates how to add and subtract signed integers on a number line by interpreting arithmetic as directed movement (position change). It highlights the key idea that negative and positive values correspond to opposite directions, so the result of “a + b” and “a − b” can be read as the endpoint after applying a directed displacement. The core math concepts include signed integers, the addition/subtraction rules, reading coordinates on a number line, and modeling algebraic operations with vector translation. Construction-wise, it uses GeoGebra commands Point, Vector, and Text: points (e.g., the given numbers and intermediate locations such as A, C, D) represent the relevant coordinates, vectors (such as u and v) encode the direction and magnitude of the signed move, and labels (Text objects like text1–text6) annotate inputs and outcomes. The objects sum and diff provide the computed endpoints for addition and subtraction. Suitable for middle school to early high school learners studying arithmetic with integers, number-line reasoning, and conceptual support for adding the opposite.