What Are Variables In Open Sentence
Till now we have learned an open number system that includes a symbol such as; or a;. Instead of these symbols, we can use variables to represent missing information. These letters are known as variables because their values can change.
In other words, a variable is a symbol that is used for a number we don’t know yet. Variables are usually represented by letters such as x or y.
If x = 2, then x + 4 = 2 + 4 = 6.
If x = 3, then x + 4 = 3 + 4 = 7.
If x = 0, then x + 4 = 0 + 4 = 0.
As you can see, the values of x are changing, and that is why it is known as variables.
Algebra With Pizzazz Answer Key
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Presentation On Theme: 1
1 13 Open SentencesIn this section we are going to define a mathematical sentence and the algebraic term solution. We will also solve equations and inequalities using replacement sets and order of operations.Algebra by Gregory HaucaGlencoe adapted from presentations by Linda Stamper
2 In section 11 we discussed the difference between phrases and sentences in English.Sentences have verbs and phrases do not.Phrases are translated into expressions. ex. 2x + 3Sentences are translated into equations and inequalities.In algebraAn equation is a mathematical sentence with the equal sign between two expressions.ex = 8,3x + 1 = 4An inequality has an inequality sign between them.ex > 0,2x + 1 < 4x – 3
3 Equations and inequalities can be either TRUE or FALSEExamples: 2 + 3 = 137 – 2 > 8 + 2= 135 > 8 + 213 = 135 > 10TrueFalseAn equation or inequality is open if it contains a variable expression.ex. 7x 2 = 8,3 < 8Open sentences are neither true nor false until the variable have been replaced by specific values and the open sentence simplified.Example: x + 3 = 5 + 3 = 55 = 5True
4 The process of finding a value for the variable that results in a true statement is called solving.This replacement value is called a solution. An equation or inequality may have one, many, or no solutions.The value or values of the variable that make an equation or inequality true is called the solution.
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Numbers Numerals And Equations
The number of eggs in this carton
A name for a number is called a numeral or a numerical expression. The open sentence x4=2 may be converted into a true statement by replacing x with any numeral that names the number of eggs in the carton pictured above. For example,
Since 542 , we say that the number 5 does not satisfy the open sentence x4=2.
Although the variable x may be replaced by many numerals to convert the open sentence x4=2 into a true statement, all such numerals are names for the same number because there is one and only one number that satisfies this open sentence. It is true that the number 6 satisfies this open sentence, and that the number 3+3 also satisfies this open sentence, but 6 and 3+3 are just different names for the same number.
The sentence 6 4 = 2 is called an equation. This equation tells us that 64 is the same number as 2. It is a true statement because the numerals 64 and 2 name the same number. The equation 5 4 = 2 is a false statement because 54 and 2 are not names for the same number.
The equation
4=4
is a true statement because 4 and 4 are names for the same number. The parentheses in the numeral 4 tell you that you may find another name for the number 4 by first adding 3 and 3 and then subtracting 4 from their sum:
The sentence=says that the set of all numbers that satisfy the equation x4=2 consists of just the number 6.
Review Of Open Sentences In Mathematics
Overview:
Open sentences in mathematics are sentences that contain variables.; They can be true or false depending upon the numbers that are substituted for the variables.; Solving open sentences to make them true is an important part of algebra.
What Are Numerical Expressions?
Numerical expressions contain numbers only, such as 4/5, 2 + 4 = 6, 3 X 2 1, and so forth.; These are closed sentences, and are either always true or always untrue .; They are evaluated by means of arithmetic.
What Are Variables?
Variables are values represented by letters within a number sentence.; For example, 3 +y =10 contains the variable y, and l w=a, contains variables l, w, and a.; The integer that equals y in the first sentence is 7, but many numbers can be substituted for l and w.; Variables are used in algebraic expressions.
What Are Equations?
Equations are number sentences that contain the equals sign, whether or not they contain variables.; For example, 2 X 2 = 4 is an equation, as is 142 = 12.; Sentences such as 2 + x =5 or 3y2 +4 =x are also equations.; Sentences do not have to be true to be equations.; For example, a sentence like 2 + 2 = 5 is an equation, even though it is false.
What Are Inequalities?
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Use The Language Of Algebra
 Mathematics at OpenStax CNX
 Use variables and algebraic symbols
 Identify expressions and equations
 Simplify expressions using the order of operations
Be Prepared!
Before you get started, take this readiness quiz.
Simplify Expressions Using The Order Of Operations
Weâve introduced most of the symbols and notation used in algebra, but now we need to clarify the order of operations. Otherwise, expressions may have different meanings, and they may result in different values.
For example, consider the expression:
Imagine the confusion that could result if every problem had several different correct answers. The same expression should give the same result. So mathematicians established some guidelines called the order of operations, which outlines the order in which parts of an expression must be simplified.
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Open Sentences With Inequality Symbols
As you can see, there are many solutions when working with inequalities. We can express all of these solutions by using the inequality symbol in our answer.
If your mental math skills are not up to par, then you may have trouble finding solutions for these math sentences. When you use integers in math sentences, then finding the solutions can be really tough. Therefore, you may want to check out our lessons on solving equations.
It’s best to start with the lesson on solving addition equations.
Always Sometimes Never True
As previously discussed, algebraic expressions are like mathematical phrases or sentences. Equations are like mathematical statements. A mathematician will always ask whether or not an equation is true.
When equations contain no unknown quantities, use calculation to check if they are true:
three plus four minus two equals six is an equation but it is not true.
equation left hand side three plus 22 equals right hand side 24 plus one is an equation that is true.
When equations include unknown quantities, they may be true for only one value of the unknown:
two times n minus five equals 17 is only true when n is 11.
If n = 10 then 2n 5 = 17 is false.
They may be true for several values:
n squared plus one equals 10 is true when n = 3 and when n = 3.
They may be true for all values of the unknown:
equation left hand side two times open n plus three close equals right hand side two times n plus six
In formal mathematics you can use the sign to show that these expressions are identically equal:
equation left hand side two times open n plus three close identical to right hand side two times n plus six
Sometimes an equation is given as a definition or a formula for working something out. We can assume that someone else has done the work of showing it is always true. For example:
equation left hand side a cubed equals right hand side a multiplication a multiplication a .
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Solve Equations Using The Subtraction Property Of Equality
Our puzzle has given us an idea of what we need to do to solve an equation. The goal is to isolate the variable by itself on one side of the equations. In the previous examples, we used the Subtraction Property of Equality, which states that when we subtract the same quantity from both sides of an equation, we still have equality.
y = 46
Simplify Expressions With Exponents
To simplify a numerical expression means to do all the math possible. For example, to simplify \ wed first multiply \ to get \ and then add the \ to get \. A good habit to develop is to work down the page, writing each step of the process below the previous step. The example just described would look like this:
Suppose we have the expression \. We could write this more compactly using exponential notation. Exponential notation is used in algebra to represent a quantity multiplied by itself several times. We write \ as \ and \ as \. In expressions such as \, the \ is called the base and the \ is called the exponent. The exponent tells us how many factors of the base we have to multiply.
means multiply three factors of \
We say \ is in exponential notation and \ is in expanded notation.
Definition: Exponential Notation
For any expression \, \ is a factor multiplied by itself \ times if \ is a positive integer.
The expression \ is read \ to the \ power.
For powers of \ and \, we have special names. \ is read as “\ squared” \ is read as “\ cubed” Table \ lists some examples of expressions written in exponential notation.
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Solve Equations Using The Addition Property Of Equality
In all the equations we have solved so far, a number was added to the variable on one side of the equation. We used subtraction to undo the addition in order to isolate the variable.
But suppose we have an equation with a number subtracted from the variable, such as We want to isolate the variable, so to undo the subtraction we will add the number to both sides.
We use the Addition Property of Equality, which says we can add the same number to both sides of the equation without changing the equality. Notice how it mirrors the Subtraction Property of Equality.
Solving Open Sentence Using Inverse Operation
An open sentence can also be solved using inverse operations. The inverse operation does the opposite of another operation. Addition and Subtraction are inverse operations, whereas Multiplication and Division are inverse operations.
For example, 7 ; 5 is the same as 7 + . The numbers 5 and – 5 are known as additive inverse. When we add 5 + , we get the answer 0.
Similarly,; 6 ÷ 2/3 is the same as 6 × 3/2. A fraction and its inverse are known as multiplicative inverse. When we multiply, 2/3 × 3/2, we get the answer 1.
Solving Open Sentence Using Inverse Operation Example
Q. Find the value of yin the open sentence:
y +; 4 = 16
Solution:
Step 1: We will use the addition and subtraction inverse operation to solve the given open sentence. Subtracting 4 from both the side, we get:
y + 4 – 4 = 16 – 4;;;;
Step 2: Simplify the equation until you get variable = value.
y + 4 – 4 = 16 – 4
y +; 0 = 12
y = 12
Hence, the value of y is 12.
Remember: An open is not considered as solved if the variable is negative. For example, – x = 6. The variable should always be positive in the final answer. For example, x = 6.
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Open Sentences In Algebra
Yes, sentences are not only used in English class, but also in Math! In algebra a sentence contains numbers, variables, operations and either an equal sign or an inequality symbol.
A sentence that contains an equal sign is called an equation. If a sentence is not an equation, then it is an inequality. Take a look at the following mathematical symbols for their corresponding meanings:
An open sentence is a sentence that contains one or more variables that may be true or false depending on what values you substitute for the variables.
Model The Subtraction Property Of Equality
We will use a model to help you understand how the process of solving an equation is like solving a puzzle. An envelope represents the variable since its contents are unknown and each counter represents one.
Suppose a desk has an imaginary line dividing it in half. We place three counters and an envelope on the left side of desk, and eight counters on the right side of the desk as in . Both sides of the desk have the same number of counters, but some counters are hidden in the envelope. Can you tell how many counters are in the envelope?
What steps are you taking in your mind to figure out how many counters are in the envelope? Perhaps you are thinking I need to remove the counters from the left side to get the envelope by itself. Those counters on the left match with on the right, so I can take them away from both sides. That leaves five counters on the right, so there must be counters in the envelope. shows this process.
What algebraic equation is modeled by this situation? Each side of the desk represents an expression and the center line takes the place of the equal sign. We will call the contents of the envelope so the number of counters on the left side of the desk is On the right side of the desk are counters. We are told that is equal to so our equation is
Lets write algebraically the steps we took to discover how many counters were in the envelope.
First, we took away three from each side. 
Then we were left with five. 
x + 1 = 7; x = 6
x + 3 = 4; x = 1
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Open Sentence In Mathematics
An open sentence in Mathematics is neither true nor false until the variables have been substituted by specific values. The method of finding the values of variables that result in a true sentence is known as solving the open sentence. The replacement value is known as the solution of the open sentence.
For example, 1 – y = 8 is an open sentence because the value of y is unknown and as a result, we can state if it is true or false.
The uncertainty that we have about 1 y = 8 is what makes 1 y = 8 an open statement.
Solving Open Sentence Using Two Operations
The open sentence may have one or more than one mathematical operations, To solve such an open sentence, you need to remember the correct order given below:

Bracket
Find the value of y ÷ 2 + 3 = 8
Solution:
Step 1:; Decide which inverse operation should be done first.
As per the BODMAS rule, you must calculate y ÷ 2; before 2 + 3. This implies y ÷ 2; must stay together. You can insert brackets to simplify the problem.
We should use inverse addition first to simplify the sentence as shown below:
+ 3 – 3 = 8 – 3
Step 2: Simplify the sentence until you left with only one operation.
+ 3 – 3 = 8 – 3
y ÷ 2; = 5
Step 3: Simplify using the inverse operation until you get the variable = value.
y ÷ 2; = 5
y ÷ 2 × 2 =; 5 × 2
y; = 10
We can use the open sentence to solve problems that are described in words. To solve problems, we need to translate the words into mathematical operation as shown below:
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The Beginnings Of Algebra
More than 3,500 years ago an Egyptian named Ahmes collected a set of mathematical problems and their solutions. Included were problems such as finding the number that satisfies the equation
x=37.
About 2,500 years ago the Greek mathematician Pythagoras started a religiousmathematical brotherhood. Its members were called Pythagoreans. Intensely interested in geometry, they classified numbers according to geometrical properties. For example, they studied properties of the triangular numbers
The famous Greek geometer Euclid discovered important properties of numbers through a study of geometry. For example, the truth of the sentence 2=+ is verified geometrically by noting that the area of the following rectangle:
Diophantus, another famous early Greek mathematician, has been called the father of algebra. He treated algebra from a purely numerical point of view. He made a special study of certain types of equations that are today called Diophantine equations.
Our modern word algebra comes from the Arabic aljabr, which appeared in the title of an algebra text written in about ad 825 by the Arab astronomer and mathematician alKhwarizmi. The words algorism and algorithm are derived from his name.