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1.3 – AXIOMS FOR THE REAL NUMBERS. Goals. SWBAT apply basic properties of real numbers SWBAT simplify algebraic expressions. An axiom (or postulate ) is a statement that is assumed to be true.
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Goals • SWBAT apply basic properties of real numbers • SWBAT simplify algebraic expressions
An axiom (or postulate) is a statement that is assumed to be true. • The table on the next slide shows axioms of multiplication and addition in the real number system. Note: the parentheses are used to indicate order of operations
Substitution Principle: • Since a + b and ab are unique, changing the numeral by which a number is named in an expression involving sums or products does not change the value of the expression. • Example: and • Use the substitution principle with the statement above.
Identity Elements In the real number system: The identity for addition is: 0 The identity for multiplication is: 1
Inverses For the real number a, The additive inverse of a is: -a The multiplicative inverse of a is:
Axioms of Equality • Let a, b, and c be and elements of . • Reflexive Property: • Symmetric Property: • Transitive Property:
The following are basic theorems of addition. Unlike an axiom, a theorem can be proven.
Theorem For all real numbers b and c,
Theorem • For all real numbers a, b, and c, • If , then
Theorem For all real numbers a, b, and c, if or then
Property of the Opposite of a Sum For all real numbers a and b, That is, the opposite of a sum of real numbers is the sum of the opposites of the numbers.
Cancellation Property of Additive Inverses For all real numbers a,
Simplify 1. 2.
Multiplication properties are similar to addition properties. • The following are theorems of multiplication.
Theorem • For all real numbers b and all nonzero real numbers c,
Cancellation Property of Multiplication • For all real numbers a and b and all nonzero real numbers c, if or ,then
Properties of the Reciprocal of a Product • For all nonzero real numbers a and b, • That is, the reciprocal of a product of nonzero real numbers is the product of the reciprocals of the numbers.
Multiplicative Property of Zero • For all real numbers a, and
Multiplicative Property of -1 • For all real numbers a, and
Properties of Opposites of Products • For all real numbers a and b,
Explain why the statement is true. 1. A product of several nonzero real numbers of which an even number are negative is a positive number.
Explain why the statement is true. 2. A product of several nonzero real numbers of which an odd number are negative is a negative number.
Simplify 3.
Simplify 8.
Simplify the rest of the questions and then we will go over them together!
The difference between a and b, , is defined in terms of addition. Definition
Definition of Subtraction • For all real numbers a and b,
Subtraction is not commutative. Example: • Subtraction is not associative. Example:
Your Turn! Try numbers 3 and 4 and we will check them together!