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Subtraction – About subtraction – pg.1/3

Posted in Math Theory by Lia on 11/17/2011

Subtraction: pg. 1, 23

Contents:

pg.1…..Subtraction  – about subtraction

pg.2…..Subtraction – exercises

pg.3…..Subtraction – answers to exercises

 

About subtraction

The result of subtraction is called the difference.

Note:

  • When a parenthesis that is preceded by a plus sign is opened, all the terms that were inside that parentheses  maintain their sign.

    Example: 7x + (3a – 5 + 4b – 2c) = 7x + 3a – 5 + 4b – 2c

  • When a parenthesis that is preceded by a minus sign is opened, all the terms that were inside that parentheses change their sign.

    Example: 5x – (4a – 3 + 2b – 5c) = 5x – 4a + 3 – 2b + 5c

 

There are more ways to subtract numbers.

The most common way is to subtract one number from the other.

Example:

*  Subtract 3 from 7.

7 – 3 = 4

*  Subtract -4 from 10.

10 – (-4) = 10 +4 = 14

*  Subtracting multiple numbers from one number:

Let’s assume that we need to subtract 6 and -4 and 1 and -2 from 13.

13 – [6+ (-4)+1+ (-2)] =13 – (6 – 4 + 1 – 2) = 13 – 1 = 12 or by opening the parentheses preceded by the minus sign,  the calculation can look like: 13 – [6+ (-4)+1+ (-2)] =13 – (6 – 4 + 1 – 2) = 13 – 6 +4 – 1 +2 = (13 – 6) + 4 – 1 + 2 = 7 + 4 – 1 + 2 = (7 + 4) – 1 + 2 = 11 -1 + 2 = (11 – 1) +2 = 10 +2 = 12

 

 

Subtraction: pg. 1, 23

 

 

 

 

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