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**1.1 Some Basics of Algebra Algebraic Expressions and Their Use**

Translating to Algebraic Expressions Evaluating Algebraic Expressions Sets of Numbers

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Terminology A letter that can be any one of various numbers is called a variable. If a letter always represents a particular number that never changes, it is called a constant.

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**Algebraic Expressions**

An algebraic expression consists of variables, numbers, and operation signs. Examples: When an equal sign is placed between two expressions, an equation is formed.

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**Translating to Algebraic Expressions**

Key Words per of less than more than ratio twice decreased by increased by quotient of times minus plus divided by product of difference of sum of divide multiply subtract add Division Multiplication Subtraction Addition

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**Example Translate to an algebraic expression:**

Eight more than twice the product of 5 and a number. Solution Eight more than twice the product of 5 and a number.

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**Evaluating Algebraic Expressions**

When we replace a variable with a number, we are substituting for the variable. The calculation that follows is called evaluating the expression.

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**Example Evaluate the expression Solution 8xz – y = 8·2·3 – 7 = 48 – 7**

Substituting = 48 – 7 Multiplying = 41 Subtracting

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Example The base of a triangle is 10 feet and the height is 3.1 feet. Find the area of the triangle. Solution h 10·3.1 b = 15.5 square feet

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**Exponential Notation n factors**

The expression an, in which n is a counting number means n factors In an, a is called the base and n is called the exponent, or power. When no exponent appears, it is assumed to be 1. Thus a1 = a.

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**Rules for Order of Operations**

1. Simplify within any grouping symbols. 2. Simplify all exponential expressions. 3. Perform all multiplication and division working from left to right. 4. Perform all addition and subtraction working from left to right.

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**Example Evaluate the expression Solution 2(x + 3)2 – 12 x2**

= 2(2 + 3)2 – Substituting Working within parentheses Simplifying 52 and 22 Multiplying and Dividing Subtracting

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**Example Evaluate the expression Solution**

4x2 + 2xy – z = 4·32 + 2·3·2 – 8 Substituting = 4·9 + 2·3·2 – 8 Simplifying 32 = – 8 Multiplying = 40 Adding and Subtracting

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Part 2 of 1.1 Sets of Numbers

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**Sets of Numbers Natural Numbers (Counting Numbers) Whole Numbers**

Numbers used for counting: {1, 2, 3,…} Whole Numbers The set of natural numbers with 0 included: {0, 1, 2, 3,…} Integers The set of all whole numbers and their opposites: {…,-3, -2, -1, 0, 1, 2, 3,…}

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**Sets of Numbers Rational Numbers**

Numbers that can be expressed as an integer divided by a nonzero integer are called rational numbers:

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**Converting Fractions to Decimals**

Divide the numerator by the denominator 4 8 2 0 1 8

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**Any fraction can be converted to a repeating decimal or a terminating decimal..**

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**Look at the following conclusion.**

All integers can be written as fractions. Insert a denominator of 1. Look at the following conclusion.

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**Rationals include the following.**

All integers (-2, 5, 17, 0) All fractions (proper, improper, or mixed) All terminating decimals All repeating decimals -2.34,

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**Sets of Numbers Real Numbers**

Numbers like are said to be irrational. Decimal notation for irrational numbers neither terminates nor repeats. Real Numbers Numbers that are either rational or irrational are called real numbers:

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**Identify as natural, whole, integers, rational, or irrational.**

-3 10 0.457 6.2

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**Answers Natural: 10 Whole: 10 0 Integers: 10 0 -3 Rational:**

Irrational:

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**Set Notation Roster notation: {2, 4, 6, 8}**

Set-builder notation: {x | x is an even number between 1 and 9} “The set of all x such that x is an even number between 1 and 9”

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**Write with Roster Notation**

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**Write with Set-Builder Notation**

1) The set of all integers between -6 and 1 5)

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Elements and Subsets If B = { 1, 3, 5, 7}, we can write B to indicate that 3 is an element or member of set B. We can also write B to indicate that 4 is not an element of set B. When all the members of one set are members of a second set, the first is a subset of the second. If A = {1, 3} and B = { 1, 3, 5, 7}, we write A B to indicate that A is a subset of B.

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**True or False? Use the following sets: N= Naturals, W = Wholes,**

Z = integers, Q = Rationals, H = Irrationals, and R = Reals

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Answers False True

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