Question

If a and b are any two real numbers, explain how you calculate the difference a - b. Be sure to include the following in your explanation.

(A) a description of the relationship between addition and subtraction
(B) how you can use a number line to help with the calculation
(C) how you can determine the sign of the result

Answer 1

- Subtraction can be thought of as the inverse operation of addition, OR as addition itself, if you look at it as adding a negative number.

- The number line allows us to interpret subtraction (or addition of a negative) geometrically; we can view it as a movement to the left on the number line with a distance equal to the number being subtracted.

- Lastly, the value of any expression a - b (where a and b are real numbers) is determined by the relative sizes of the numbers. If a > b, then a - b > 0 (a positive result). If b > a, then a - b < 0 (a negative result.