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The Real Number System
Basic Concepts of Algebra
26
Mathematics
Undergraduate 1
03/18/2008

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Cards

Term

 

 

 

Rational Numbers

Definition
 
 
Numbers that can be expressed in the form p/q, where p and q are integers and q ≠ 0.  Decimal notation for rational numbers either terminates or repeats.
Term

 

 

 

Irrational Numbers

Definition
 
 
The real numbers that are not rational numbers.  Decimal notation for irrational numbers neither terminates nor repeats. 
Term

 

 

 

Real Numbers

Definition
 
 
The set of all rational numbers combined with the set of all irrational numbers.  Real numbers are modeled using a number line. 
Term

 

 

 

element

Definition
 
 
 
A member belonging to a set. 
Term

 

 

 

subset

Definition

 

 

 

When all the elements of one set are elements of a second set, the first set is a subset of the second set.

Term

 

 

 

Interval Notation

Definition
Open          (a,b)            {x | a < x < b}
Closed        [a,b]               {x | a xb}
Half-open   [a,b)               {x | a x < b}
Half-open   (a,b]               {x | a < xb}
Open          (a,∞)              {x | x > a}
Half-open   [a,∞)              {x | x a}
Open          (-∞,b)            {x | x < b}
Half-open   (-∞,b]             {x | xb}    
Term

 

 

 

Commutative Properties of 

Addition and Multiplication

Definition

 

 

 

a + b = b + a

ab = ba

Term

 

 

 

Associative Properties of

Addition and Multiplication

Definition

 

 

 

a + (b + c) = (a + b) + c

a(bc) = (ab)c

Term

 

 

 

Additive Identity Property

Definition

 

 

 

a + 0 = 0 + a = a

Term

 

 

 

Additive Inverse Property

Definition

 

 

 

-a + a = a + (-a) = 0

Term

 

 

 

Multiplicative Identity Property

Definition

 

 

 

a · 1 = 1 · a = a

Term

 

 

 

Multiplicative Inverse Property

Definition

 

 

 

a · 1/a = 1/a · a = 1  (a ≠ 0) 

Term

 

 

 

Distributive Property

Definition

 

 

 

a(b + c) = ab + ac

Term

 

 

 

Absolute Value

Definition

 

 

|a| = a if a ≥ 0

|a| = -a if a < 0

Term

 

 

 

Distance Between Two Points

on the Number Line

Definition

 

 

For any real numbers a and b, the distance between a and b is

|a - b| or equivalently, |b - a|.

Term

 

 

 

Absolute Value of a Product

Definition

 For any real numbers a and b and any nonzero number c:

 

 

|ab| = |a| · |b|.

Term

 

 

 

Absolute Value of a Quotient

Definition

 For any real numbers a and b and any nonzero number c:

 

 

|a/c| = |a| / |c|.

Term

 

 

 

Absolute Value of an Exponent

Definition
For any real numbers a and b and any nonzero number c:
 
 
|an| = an if n is an even integer.
Term

 

 

 

Absolute Value of Negative and Positive Numbers

Definition

For any real numbers a and b and any nonzero number c:

 

 

|-a| = |a|.

 

 

 

Term

 

 

 

Multiplying by -1

Definition

 

For any real number a,

 

-1 · a = -a

 

(Multiplying a number by -1 produces its opposite.)

 

 

 

Term

 

 

 

Opposites

Definition

 

For any real number a,

 

- (-a) = a

 

(The opposite of the opposite of a number is the number itself.)

Term

 

 

 

Adding Two Real Numbers

Definition
  1. Positive numbers: Add the numbers.  The result is positive.
  2. Negative numbers: Add the absolute values.  Make the answer negative.
  3. A positive and a negative number: Subtract the smaller absolute value from the larger.  Then:
    1. If the positive number is the greater absolute value, make the answer positive.
    2. If the negative number has the greater absolute value, make the answer negative.
    3. If the numbers have the same absolute value, make the answer 0.
  4. One number is zero: The sum is the other number.
Term

 

 

 

Natural Numbers

Definition

 

 

 

Those numbers used for counting {1, 2, 3, . . . }

Term

 

 

 

Whole Numbers

Definition

 

 

 

The natural numbers and 0 {0, 1, 2, 3, . . . } 

Term

 

 

 

Integers

Definition

 

 

 

The whole numbers and their opposites

{. . . -3, -2, -1, 0, 1, 2, 3, . . .}.

Term

 

 

 

roster method

Definition

 

 

 

A method of denoting sets.

e.g., a set containing the numbers 2, 3, 4, and 5 can

be written using the roster method: {2, 3, 4, 5}.

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