Thursday, September 9, 2010

"I need help with integers. what is the rule in subtracting and adding them?" by Rowlanda

"Hi ms.young i need help with integers. what is the rule in subtracting and adding them?"

Hi, Rowlanda. The rules for adding integers are as follows:

  • If the signs are the same, add and keep the sign.

Examples:

4 + 5 = 9

-4 + (-3) = -7

-4 - 4 = -8 (this one is tricky, but remember + (-4) and -4 means the same thing)

  • If  the signs are different, subtract the digits and keep the sign of the "larger" number.
Examples:

-9 + 5 = -4

9 + (-4) = 5 (Remember: this means the same thing as " 9 - 4 ")

The one that confuses students is the following:

-7 - (-2); this is better understood as  -7 + 2 because "the opposite of negative 2" [-(-2)] is positive 2.
once this is rewritten, just follow your rules to arrive at the answer of -5.

Get it?  Good!

Mrs. Young