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### Drawing Equations on the Number Line

```Date: 05/09/2002 at 01:21:46
From: Toni Balmer
Subject: integers

I can't figure out how to draw a certain equation on a number
line.

2 +   5  =  7  is easy
-2 +   5  =  3  is easy
2 + (-5) = -3  is easy

but I get stuck on

2 - (-5) =  7

I know that I will change the signs and add, but how do I show
this on a number line?
```

```
Date: 05/09/2002 at 12:18:45
From: Doctor Peterson
Subject: Re: integers

Hi, Toni.

You have to decide how to represent subtraction. One way is to
say that, whereas you add by putting two "arrows" head to tail:

o---------->                    5
o---------------> + 7
o--------------------------->  12

you subtract by following the second arrow backwards, putting
first to the tail of the second:

o--------------------------->  12
o---------------> - 7
o---------->                    5

Now if you subtract a negative number, it looks like this:

o---------->                     5
<---------------o - -7
o--------------------------->   12

Do you see how this is the same as changing the subtraction of -7
to addition of +7?

- Doctor Peterson, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
Elementary Subtraction
Middle School Graphing Equations
Middle School Negative Numbers

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