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| 14 Theory slides |
| 9 Exercises - Grade E - A |
| Each lesson is meant to take 1-2 classroom sessions |
Here is a recommended reading before getting started with this lesson.
Sometimes a quantity is unknown or its value may change. If this is the case, the best way to represent this quantity is using a variable.
There are many real-life situations that can be modeled by combining numbers and variables in algebraic expressions. A special case of algebraic expressions are linear expressions.
A linear term is an algebraic expression that includes a coefficient multiplied by a variable with an exponent of one. A linear expression is an expression that includes at least one linear term and any constant terms. No other type of terms may be included. The most common form of a linear expression is given below.
In this expression, a and b are real numbers, with a=0. To completely understand the definition of a linear expression, some important concepts will be be broken down. Consider the example linear expression x−5y+2.
x−5y+2 | ||
---|---|---|
Concept | Explanation | Example |
Term | Parts of an expression separated by a +or −sign. |
x, -5y, 2 |
Coefficient | A constant that multiplies a variable. If a coefficient is 1, it does not need to be written due to the Identity Property of Multiplication. | 1, -5 |
Linear Term | A term that contains exactly one variable whose exponent is 1. | x, -5y |
Constant Term | A term that contains no variables. It consists only of a number with its corresponding sign. | 2 |
The following table shows some examples of linear and non-linear expressions.
Linear Expressions | Non-linear Expressions |
---|---|
3x | 5 |
-5y+1 | 2xy−3 |
3x−21y+2 | x1−2 |
πx+6y | 5x2+x−1 |
Ramsha, Tiffaniqua, Zosia, and some of their friends are spending the summer at math camp. One of their first lessons is about identifying parts of linear expressions. They are given the following table to fill in based on the linear expressions in the top row.
6x−1 | 2+x | -2x+3−9y | |
---|---|---|---|
Term(s) | |||
x-term | |||
y-term | |||
Linear Term(s) | |||
Coefficient(s) | |||
Constant Term |
Help them fill in the table.
6x−1 | 2+x | -2x+3−9y | |
---|---|---|---|
Term(s) | 6x and -1 | 2 and x | -2x, 3, and -9y |
x-term | 6x | x | -2x |
y-term | - | - | -9y |
Linear Term(s) | 6x | x | -2x and -9y |
Coefficient(s) | 6 | 1 | -2 and -9 |
Constant Term | -1 | 2 | 3 |
When there is no number in front of a variable, the coefficient is 1. The x- and y-terms are the terms that contain the variables x and y, respectively.
Start by finding the terms of each expression. Recall that the terms are the parts separated by addition or subtraction signs.
6x−1 | 2+x | -2x+3−9y | |
---|---|---|---|
Term(s) | 6x and -1 | 2 and x | -2x, 3, and -9y |
x-term | |||
y-term | |||
Linear Term(s) | |||
Coefficient(s) | |||
Constant Term |
The x-term is the term that contains the variable x.
6x−1 | 2+x | -2x+3−9y | |
---|---|---|---|
Term(s) | 6x and -1 | 2 and x | -2x, 3, and -9y |
x-term | 6x | x | -2x |
y-term | |||
Linear Term(s) | |||
Coefficient(s) | |||
Constant Term |
Similarly, the y-term is the term that contains the variable y. In this case, the first two expressions do not have a y-term.
6x−1 | 2+x | -2x+3−9y | |
---|---|---|---|
Term(s) | 6x and -1 | 2 and x | -2x, 3, and -9y |
x-term | 6x | x | -2x |
y-term | - | - | -9y |
Linear Term(s) | |||
Coefficient(s) | |||
Constant Term |
The linear terms are the terms that contain only one variable, raised to the power of 1.
6x−1 | 2+x | -2x+3−9y | |
---|---|---|---|
Term(s) | 6x and -1 | 2 and x | -2x, 3, and -9y |
x-term | 6x | x | -2x |
y-term | - | - | -9y |
Linear Term(s) | 6x | x | -2x and -9y |
Coefficient(s) | |||
Constant Term |
Next, the coefficients are the numbers that multiply a variable. When there is no number in front of a variable, the coefficient is 1.
6x−1 | 2+x | -2x+3−9y | |
---|---|---|---|
Term(s) | 6x and -1 | 2 and x | -2x, 3, and -9y |
x-term | 6x | x | -2x |
y-term | - | - | -9y |
Linear Term(s) | 6x | x | -2x and -9y |
Coefficient(s) | 6 | 1 | -2 and -9 |
Constant Term |
Finally, the constant term is any term without a variable.
6x−1 | 2+x | -2x+3−9y | |
---|---|---|---|
Term(s) | 6x and -1 | 2 and x | -2x, 3, and -9y |
x-term | 6x | x | -2x |
y-term | - | - | -9y |
Linear Term(s) | 6x | x | -2x and -9y |
Coefficient(s) | 6 | 1 | -2 and -9 |
Constant Term | -1 | 2 | 3 |
Select the required parts of the given linear expressions.
Ramsha is on the second day of a hiking excursion at math camp. On the first day, she hiked from base camp to the first station.
Note that 1.5x+10 represents a distance and the units of each term are miles. However, the units of x are hours. This gives a clue of the units of the coefficient 1.5.
In order to get rid of hours
and end up with miles,
the units of the coefficient must be miles per hour.
Therefore, the coefficient represents speed, or more precisely, the speed at which Ramsha walks.
In the previous example, an expression modeling a real-life scenario was provided. However, most of the time such expressions are not provided and must instead be created. The use of inductive reasoning can help with this process.
n | Number of Cubes | |
---|---|---|
Figure 1 | 0 | 1+3⋅0=1 |
Figure 2 | 1 | 1+3⋅1=4 |
Figure 3 | 2 | 1+3⋅2=7 |
Figure 4 | 3 | 1+3⋅3=10 |
Figure 121 | 120 | 1+3⋅120=361 |
At the end of the math camp, the students all visit an amusement park. Tiffaniqua did so well at camp that she won a coupon that allows her entire friend group to go on rides for x dollars per ride. By the end of the day, the group has gone on 11 rides and each person has eaten one hot dog.
The total amount of money paid is the sum of the amount paid for the 11 rides and the amount spent in hot dogs. The cost per person is the total cost divided by the number of people.
In the previous two examples, each situation was represented by an algebraic expression. There are some cases where writing an expression is not enough to model a situation. In such cases, an equation might be required.
Equations always contain an equals sign, while expressions do not. In fact, an equation can be seen like a statement that connects two expressions with an equals sign.
When learning about equations, a good first step is to start with linear equations, which involve only one variable.
A linear equation is an equation with at least one linear term and any number of constants. No other types of terms may be included. Linear equations in one variable have the following form, where a and b are real numbers and a=0.
Zosia's savings can be modeled by a linear expression of the form at+b, where a and b are real numbers.
0.5t+15=25
What is the coefficient for the x-term in this situation?
Notice how the number of people sat increases with each table added.
Begin by making sense of the situation. At least 1 table is needed for the family dinner. In this case, 4 people can be seated.
For each subsequent table, two more people are seated.
Translate each sentence into an equation.
Every equation has an equals sign and values or expressions on either side of it. Key phrases such as is,
is equal to,
and equals
tell us about the placement of the equals sign.
The sum of5and two timesy = 2
On the left-hand side, we have two key phrases, sum
and times.
These phrases tell us the operations that will be used in our equation. Times
indicates multiplication, while sum
indicates addition.
The sum of 5 and two times y
5 + 2 y
On the right-hand side, we have only 2, so we can now complete the equation.
5 + 2 y = 2
Let's begin by placing the equals sign according to the sentence.
Five timesaless than3 = 7
On the left-hand side, we have two key phrases, times
and less than.
These phrases tell us the operations that will be used in our equation. Times
indicates multiplication, while less than
indicates subtraction.
Five times a less than 3
3 - 5 a
On the right-hand side, we have only 7, so we can now complete the equation.
3 - 5 a = 7
Translate each sentence into an equation.
Every equation has an equals sign and values or expressions on either side of it. Key phrases such as is,
is equal to,
and equals
tell us about the placement of the equals sign.
The sum ofpand4 = two timesp
On the left-hand side, we have the key phrase sum.
This phrase tells us which operation that will be used in our equation — in this case, addition.
The sum of p and 4
p + 4
On the right-hand side, we have the key phrase times.
This indicates multiplication.
two times p
2 p
We can now complete the equation.
p + 4 = 2 p
Let's begin by placing the equals sign according to the sentence.
Three times the sum ofaandb = 9
On the left-hand side, we have two key phrases, times
and sum.
The word times
indicates multiplication, while sum
indicates addition. In this case, the multiplication is of the whole sum of a and b, so parentheses must be added.
Three times the sum of a and b
3 ( a + b )
We have only 9 on the right-hand side, so we can now complete the equation.
3 ( a + b ) = 9
Every equation has an equals sign and values or expressions on either side of it. The given equation is no different, so let's begin our translation by using phrases such as is,
is equal to,
and equals
to express equality.
3x+5 = 9
3x+5 equals9
Now, to translate the left- and right-hand sides of this equation, let's break down the expressions and verbally express the individual terms and factors.
Algebraic Term | Verbal Translation |
---|---|
3 x | Three times x |
+ | increased by |
5 | 5 |
= | equals |
9 | 9 |
Three times x increased by 5 equals 9 |
The answer is option C. Note that because there are often several ways to express certain mathematical operations, this answer is only one of many correct ways to verbally express this equation.
Every equation has an equals sign and values or expressions on either side of it. The given equation is no different, so let's begin our translation by using phrases such as is,
is equal to,
and equals
to express equality.
7(a+2) = b-3
7(a+2) is equal to b-3
Now, to translate the left- and right-hand sides of this equation, let's break down the expressions and verbally express the individual terms and factors.
Algebraic Term | Verbal Translation |
---|---|
7( a + 2) | Seven times the sum of a and 2 |
= | is equal to |
b | b |
- | decreased by |
3 | 3 |
Seven times the sum of a and 2 is equal to b decreased by 3 |
The answer is option A. Note that because there are often several ways to express certain mathematical operations, this answer is only one of many correct ways to verbally express this equation.
Our formula will be expressed as an equation. Every equation has an equals sign and values or expressions on either side of it. Key phrases such as is,
is equal to,
and equals
tell us about the placement of the equals sign.
The perimeter P of a regular hexagon = 6times the lengths of each side.
On the left-hand side, we only have the perimeter P.
The perimeter P of a regular hexagon
P
Now we will take care of the right-hand side.
6times the length s of each side
6times s
We also have a single key word on the right-hand side, times.
This indicates multiplication.
6times s
6 s
Putting these sides together, we have a complete formula.
P = 6 s