Lesson How to Add and Subtract Negative Numbers

Source code of 'How to Add and Subtract Negative Numbers'

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<center><a href = "http://www.mathick.com/mathick.php?topic=addnegs">Try a sample problem!</a>

<table cellspacing = '5' cellpadding = '5' border = '10'><tr> <td>Problem:</td>	 	 <td><center>3 + +5</center></td> <td><center>3 + (-5)</center></td> 	 <td><center>3 - (+5)</center></td> 	 <td><center>3 - -5</center></td> <td><center>-3 + (-5)</center></td> 	 <td><center>-3 - -5</center></td></tr><tr> <td>If you see two signs next to each other,
change them to a single sign:

<center>++ changes to +
+- changes to -
-+ changes to -
 -- changes to +</center></td> 	 <td><center>3 + 5</center></td><td><center>3 - 5</center></td> <td><center>3 - 5</center></td> 	 <td><center>3 + 5</center></td 	 <td><center>3 + 5</center></td> <td><center>-3 - 5</center></td> 	 <td><center>-3 + 5</center></td></tr><tr> <td>Now there are just two signs.
(For example, 3-5 is really +3 - 5)

If the 2 signs are different,
the answer has the sign of the larger number.
(5 in this case, since 5 is larger than 3.)

If they're the same, the answer also has the same sign. </td>	 <td><center>+</center></td> 	 <td><center>-</center></td> 	 <td><center>-</center></td> 	 <td><center>+</center></td> 	 <td><center>-</center></td> <td><center>+</center></td></tr><tr> <td>If the signs are different, subtract the two numbers.
If they're the same, add.</td> 	 <td><center>8</center></td> 	 <td><center>2</center></td> 	 <td><center>2</center></td> 	 <td><center>8</center></td>	 <td><center>8</center></td> 	 <td><center>2</center></td></tr><tr> <td>Final Answer:</td> 	 <td><center>+8</center></td> 	 <td><center>-2</center></td> 	 <td><center>-2</center></td> 	 <td><center>+8</center></td> 	 <td><center>-8</center></td> 	 <td><center>+2</center></td></tr></table>