Question 800147: If a and b are any two real numbers, explain how you calculate the difference a-b. Be sure to include the following in the explanation.
A) A description of the relashionship between addition and subtraction.
B) How you can use a numberline to help with the calculation.
C) How you can determine the sign of the result.
Answer by rothauserc(4718)   (Show Source):
You can put this solution on YOUR website! If a and b are real numbers, a−b is the same as a+(−b), where −b is the opposite of b.
consider the number line
-1 0 1 2 3 4 5 6
we now use the above number line to illustrate that the subtraction 5−2 produces 3, that is, 5−2=3
We begin at 0, the origin.
Since 5 is positive, we move 5 units to the right.
Then, we move 2 units to the left to get to 3. (This reminds us of addition with a negative number.)
This illustration suggests that 5−2 is the same as 5+(−2).
Clearly if the result of the subtraction process is to the right of the origin, the sign is positive. Also, if the result of the subtraction process is to the left of the origin, the sign is negative.
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