Signed Numbers and Algebraic Thinking

Abstract

Signed numbers are positive and negative numbers. They refer to integers, notmerely the natural numbers or positive integers. They refer to rational numbers,not merely the non-negative rational numbers. They refer to real numbers, notmerely non-negative real numbers. Students may learn to accept negative num-bers in the co-domain (output of computations) before accepting them in thedomain (input of computations). When they are comfortable with both, we saythey have learned not only that signed numbers exist, but they can serve asthe input for addition, subtraction, multiplication, and division as well as otherfunctions.