Numerical Operations

A numerical operation can be described as an action or process used to solved a numerical problem.

Adding and Subtracting Signed Numbers 

If you have two numbers x and y, the following rules apply when these numbers are being added or subtracted.

• Rule of Signs for Addition:   (x – y) is the same as x + (–y)  or  x – (+y) because a negative beside a positive (or vice versa) always make a negative.
• Rule of Signs for Subtraction:   x + y is the same as x – (–y) because two negatives side-by-side make a positive.

Here are a few examples:

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For #1, the answer is clearly 9. But you could also have gotten 9 if you had:   7 – (–2) because of the rule of signs for subtraction.

For #2, the answer is 5. But you could also have gotten 5 if you had:   9 + (–4) or 9 – (+4) because of the rule of signs for addition.

For #3, the answer is –2.

A summary of these symbols is shown below:

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More examples: null

Multiplying and Dividing Signed Numbers 

• Rules of Signs for Multiplication:   
  • (+x)(+y) = (–x)(–y) = +xy
  • (+x)(–y) = (–x)(+y) = –xy
• It’s also important to note that the same rules apply for division too.

Multiplication of two or more factors can be symbolized in 3 main ways:

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For division:

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Here are a few examples:

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