Fundamentals of Mathematics, 2008a

584 CHAPTER 10. SIGNED NUMBERS
10.3 Signed Numbers 3
10.3.1 Section Overview
• Positive and Negative Numbers
• Reading Signed Numbers
• Opposites
• The Double-Negative Property
10.3.2 Positive and Negative Numbers
Positive and Negative Numbers
Each real number other than zero has a sign associated with it. A real number is said to be a positive
number if it is to the right of 0 on the number line and negative if it is to the left of 0 on the number line.
note: + and − Notation
A number is denoted as positive if it is directly preceded by a plus sign or no sign at all.
A number is denoted as negative if it is directly preceded by a minus sign.
10.3.3 Reading Signed Numbers
The plus and minus signs now have two meanings:
The plus sign can denote the operation of addition or a positive number.
The minus sign can denote the operation of subtraction or a negative number.
To avoid any confusion between "sign" and "operation," it is preferable to read the sign of a number as
"positive" or "negative." When "+" is used as an operation sign, it is read as "plus." When "−" is used as
an operation sign, it is read as "minus."
10.3.3.1 Sample Set A
Read each expression so as to avoid confusion between "operation" and "sign."
Example 10.6
−8 should be read as "negative eight" rather than "minus eight."
Example 10.7
4 + (−2) should be read as "four plus negative two" rather than "four plus minus two."
Example 10.8
−6 + (−3)should be read as "negative six plus negative three" rather than "minus six plus minus
three."
Example 10.9
−15−(−6)should be read as "negative fteen minus negative six" rather than "minus fteen minus
minus six."
Example 10.10
−5 + 7 should be read as "negative ve plus seven" rather than "minus ve plus seven."
Example 10.11
0 − 2 should be read as "zero minus two."
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