9.1 Rational Numbers
 
Real Number Line 

-4       -3          -2   -1        0        ½          1      2         3          4 
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Negative real numbers                 Zero(neither + or -)       Positive real numbers

    Set of Rational Numbers

        Real numbers {Rational Numbers{Fraction / Integers{Whole numbers{Counting}, 0}} }

        Real numbers {Irrational numbers}

    Definition Rational Numbers: {fractions, whole numbers (), integers}

        The set of rational numbers is : Q={
 
Equality of Rationals: Definition

Equality Theorem: n = nonzero integer

(smiplest form: lowest term)

Addition of Rationals: Definition

Additive Inverse Theorem: 

(note -b hard to interpret)

Properties (Rational Numbers Addition):
 
Closure: Fract. X Fract. = Fract.

Cumutative:

Associative:

Additive Inverse:

Identity:

 
Theorem:Additive cancellation

Opposite of Opposite:

Subtraction: Adding Opp.

(common / uncommon denominators)

 
Multiplcation of Rational Numbers

                

    Properties (Rational Numbers Multiplication):
 
Closure: Fract. X Fract. = Fract.

Cumutative:

Distributive of Multiplication / Addition:

Multiplication Inverse: (Theorem)

Every ratitionals  has a unique rationals such that: (reciprocal)

Identity:

Associative:

Division of Rational Numbers

                

Division of Rationals: Theorem

                1. 

                2.

                3.

Ordering of Rationals:

        Number line approach

        Common-positive denominator a/b > c/d ifi a > c

        Additive approach
 

Cross-Multiplication Theorem: (for b > 0 and d > 0)