Lesson 8: Linear Equations in Disguise

13
Lesson 8: Linear Equations in Disguise Date: 11/8/13 79 Β© 2013 Common Core, Inc. Some rights reserved. commoncore.org This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8 Lesson 8: Linear Equations in Disguise Student Outcomes Students rewrite and solve equations that are not obviously linear equations using properties of equality. Lesson Notes In this lesson, students learn that some equations that may not look like linear equations are, in fact, linear. This lesson on solving rational equations is included because of the types of equations students will see in later topics of this module related to slope. Students will recognize these equations as proportions. It is not necessary to refer to these types of equations as equations that contain rational expressions. They can be referred to simply as proportions since students are familiar with this terminology. Expressions of this type will be treated carefully in algebra as they involve a discussion about why the denominator of such expressions cannot be equal to zero. That discussion is not included in this lesson. Classwork Concept Development (3 minutes) Some linear equations may not look like linear equations upon first glance. A simple example that you should recognize is 5 = 6 12 What do we call this kind of problem and how do we solve it? This is a proportion. We can solve this by multiplying both sides of the equation by 5. We can also solve it by multiplying each numerator with the other fraction’s denominator. Students may not think of multiplying each numerator with the other fraction’s denominator because multiplying both sides by 5 requires fewer steps and uses the multiplication property of equality that has been used to solve other equations. If necessary, state the theorem and give a brief explanation. Theorem. Given rational numbers , , , and , so that β‰  0 and β‰  0, the property states If = , then = . To find the value of , we can multiply each numerator by the other fraction’s denominator. 5 = 6 12 12 = 6(5)

Transcript of Lesson 8: Linear Equations in Disguise

Lesson 8: Linear Equations in Disguise Date: 11/8/13

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

Lesson 8: Linear Equations in Disguise

Student Outcomes

Students rewrite and solve equations that are not obviously linear equations using properties of equality.

Lesson Notes In this lesson, students learn that some equations that may not look like linear equations are, in fact, linear. This lesson on solving rational equations is included because of the types of equations students will see in later topics of this module related to slope. Students will recognize these equations as proportions. It is not necessary to refer to these types of equations as equations that contain rational expressions. They can be referred to simply as proportions since students are familiar with this terminology. Expressions of this type will be treated carefully in algebra as they involve a discussion about why the denominator of such expressions cannot be equal to zero. That discussion is not included in this lesson.

Classwork Concept Development (3 minutes)

Some linear equations may not look like linear equations upon first glance. A simple example that you should recognize is

π‘₯5

=6

12

What do we call this kind of problem and how do we solve it?

This is a proportion. We can solve this by multiplying both sides of the equation by 5. We can also solve it by multiplying each numerator with the other fraction’s denominator.

Students may not think of multiplying each numerator with the other fraction’s denominator because multiplying both sides by 5 requires fewer steps and uses the multiplication property of equality that has been used to solve other equations. If necessary, state the theorem and give a brief explanation.

Theorem. Given rational numbers 𝐴, 𝐡, 𝐢, and 𝐷, so that 𝐡 β‰  0 and 𝐷 β‰  0, the property states

If 𝐴𝐡

=𝐢𝐷

, then 𝐴𝐷 = 𝐡𝐢.

To find the value of π‘₯, we can multiply each numerator by the other fraction’s denominator. π‘₯5

=6

12

12π‘₯ = 6(5)

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

It should be more obvious now that we have a linear equation. We can now solve it as usual using the properties of equality.

12π‘₯ = 30

π‘₯ =3012

π‘₯ =52

In this lesson, our work will be similar, but the numerator and/or the denominator of the fractions may contain more than one term. However, the way we solve these kinds of problems remain the same.

Example 1 (5 minutes)

Given a linear equation in disguise, we will try to solve it. To do so, we must first assume that the following equation is true for some number π‘₯.

π‘₯ βˆ’ 12

=π‘₯ + 1

34

We want to make this equation look like the linear equations we are used to. For that reason, we will multiply both sides of the equation by 2 and 4, as we normally do with proportions:

2 οΏ½π‘₯ +13οΏ½ = 4(π‘₯ βˆ’ 1)

Is this a linear equation? How do you know?

Yes, this is a linear equation because the expressions on the left and right of the equal sign are linear expressions.

Notice that the expressions that contained more than one term were put in parentheses. We do that so we don’t make a mistake and forget to use the distributive property.

Now that we have a linear equation. We will use the distributive property and solve as usual.

2 οΏ½π‘₯ +13οΏ½ = 4(π‘₯ βˆ’ 1)

2π‘₯ +23

= 4π‘₯ βˆ’ 4

2π‘₯ βˆ’ 2π‘₯ +23

= 4π‘₯ βˆ’ 2π‘₯ βˆ’ 4 23

= 2π‘₯ βˆ’ 4 23

+ 4 = 2π‘₯ βˆ’ 4 + 4 143

= 2π‘₯ 12β‹…

143

=12β‹… 2π‘₯

73

= π‘₯

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

How can we verify that 73

is the solution to the equation?

We can replace π‘₯ with 73

in the original equation:

π‘₯ βˆ’ 12

=π‘₯ + 1

34

73 βˆ’ 1

2=

73 + 1

34

43 2

= 83

4

4 οΏ½43οΏ½ = 2 οΏ½

83οΏ½

163

=163

Since 73

made the equation true, then we know it is the solution to the equation.

Example 2 (4 minutes)

Can we solve the following equation? Explain. 15 βˆ’ π‘₯

7=

2π‘₯ + 93

We need to multiply each numerator with the other fraction’s denominator.

So, 15 βˆ’ π‘₯

7=

2π‘₯ + 93

7(2π‘₯ + 9) = 3 οΏ½15βˆ’ π‘₯οΏ½

What would be the next step?

Use the distributive property.

Now we have

7(2π‘₯ + 9) = 3 οΏ½15βˆ’ π‘₯οΏ½

14π‘₯ + 63 =35βˆ’ 3π‘₯

Is this a linear equation? How do you know? Yes, this is a linear equation because the left and right side are linear expressions.

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

Example 3 (5 minutes)

Can we solve the following equation? If so, go ahead and solve it. If not, explain why not.

Example 3

Can this equation be solved?

πŸ” + 𝒙

πŸ•π’™ + πŸπŸ‘

=πŸ‘πŸ–

Give students a few minutes to work. Provide support to students as needed.

Yes, we can solve the equation because we can multiply each numerator with the other fraction’s denominator and then use the distributive property to begin solving it:

πŸ” + 𝒙

πŸ•π’™ + πŸπŸ‘

=πŸ‘πŸ–

(πŸ”+ 𝒙)πŸ– = οΏ½πŸ•π’™ +πŸπŸ‘οΏ½πŸ‘

πŸ’πŸ– + πŸ–π’™ = πŸπŸπ’™ + 𝟐 πŸ’πŸ–+ πŸ–π’™ βˆ’ πŸ–π’™ = πŸπŸπ’™ βˆ’ πŸ–π’™ + 𝟐

πŸ’πŸ– = πŸπŸ‘π’™ + 𝟐 πŸ’πŸ– βˆ’ 𝟐 = πŸπŸ‘π’™ + 𝟐 βˆ’ 𝟐

πŸ’πŸ” = πŸπŸ‘π’™ πŸ’πŸ”πŸπŸ‘

= 𝒙

Example 4 (5 minutes)

Can we solve the following equation? If so, go ahead and solve it. If not, explain why not.

Example 4

Can this equation be solved?

πŸ•πŸ‘π’™ + πŸ—

=πŸπŸ–

Give students a few minutes to work. Provide support to students as needed.

Yes, we can solve the equation because we can multiply each numerator with the other fractions denominator and then use the distributive property to begin solving it.

πŸ•

πŸ‘π’™ + πŸ—=πŸπŸ–

πŸ•(πŸ–) = (πŸ‘π’™ + πŸ—)𝟏 πŸ“πŸ” = πŸ‘π’™ + πŸ—

πŸ“πŸ” βˆ’ πŸ— = πŸ‘π’™ + πŸ— βˆ’ πŸ— πŸ’πŸ• = πŸ‘π’™ πŸ’πŸ•πŸ‘

= 𝒙

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

Example 5 (5 minutes)

Example 5

In the diagram below, β–³ 𝑨𝑩π‘ͺ~ β–³ 𝑨′𝑩′π‘ͺβ€². Using what we know about similar triangles, we can determine the value of 𝒙.

Begin by writing the ratios that represent the corresponding sides.

𝒙 βˆ’ πŸπŸ—.πŸ“

=𝒙 + 𝟐𝟏𝟐

It is possible to write several different proportions in this case. If time, discuss this fact with students.

Now that we have the ratios, solve for π‘₯ and find the lengths of 𝐴𝐡 and 𝐴𝐢.

𝒙 βˆ’ πŸπŸ—.πŸ“

=𝒙 + 𝟐𝟏𝟐

(𝒙 βˆ’ 𝟐)𝟏𝟐 = πŸ—.πŸ“(𝒙 + 𝟐) πŸπŸπ’™ βˆ’ πŸπŸ’ = πŸ—.πŸ“π’™ + πŸπŸ—

πŸπŸπ’™ βˆ’ πŸπŸ’+ πŸπŸ’ = πŸ—.πŸ“π’™ + πŸπŸ—+ πŸπŸ’ πŸπŸπ’™ = πŸ—.πŸ“π’™ + πŸ’πŸ‘

πŸπŸπ’™ βˆ’ πŸ—.πŸ“π’™ = πŸ—.πŸ“π’™ βˆ’ πŸ—.πŸ“π’™ + πŸ’πŸ‘ 𝟐.πŸ“π’™ = πŸ’πŸ‘

𝒙 =πŸ’πŸ‘πŸ.πŸ“

𝒙 = πŸπŸ•.𝟐

The length of |𝑨𝑩| = πŸπŸ“.𝟐 cm and the length of |𝑨π‘ͺ| = πŸπŸ—.𝟐 cm.

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

Exercises 1–4 (8 minutes)

Students complete Exercises 1–4 independently.

Exercises 1–4

Solve the following equations of rational expressions, if possible.

1. πŸπ’™+πŸπŸ—

= πŸβˆ’π’™πŸ”

Sample student work: πŸπ’™ + πŸπŸ—

=𝟏 βˆ’ π’™πŸ”

πŸ—(𝟏 βˆ’ 𝒙) = (πŸπ’™ + 𝟏)πŸ” πŸ— βˆ’ πŸ—π’™ = πŸπŸπ’™ + πŸ”

πŸ— βˆ’ πŸ—π’™ + πŸ—π’™ = πŸπŸπ’™ + πŸ—π’™ + πŸ” πŸ— = πŸπŸπ’™ + πŸ”

πŸ— βˆ’ πŸ” = πŸπŸπ’™ + πŸ” βˆ’ πŸ” πŸ‘ = πŸπŸπ’™ πŸ‘πŸπŸ

=𝟐𝟏𝟐𝟏

𝒙 πŸπŸ•

= 𝒙

2. πŸ“+πŸπ’™πŸ‘π’™βˆ’πŸ

= πŸ”πŸ•

Sample student work: πŸ“+ πŸπ’™πŸ‘π’™ βˆ’ 𝟏

=πŸ”πŸ•

(πŸ“+ πŸπ’™)πŸ• = (πŸ‘π’™ βˆ’ 𝟏)πŸ” πŸ‘πŸ“ + πŸπŸ’π’™ = πŸπŸ–π’™ βˆ’ πŸ”

πŸ‘πŸ“ βˆ’ πŸ‘πŸ“ + πŸπŸ’π’™ = πŸπŸ–π’™ βˆ’ πŸ” βˆ’ πŸ‘πŸ“ πŸπŸ’π’™ = πŸπŸ–π’™ βˆ’ πŸ’πŸ

πŸπŸ’π’™ βˆ’ πŸπŸ–π’™ = πŸπŸ–π’™ βˆ’ πŸπŸ–π’™ βˆ’ πŸ’πŸ βˆ’πŸ’π’™ = βˆ’πŸ’πŸ βˆ’πŸ’βˆ’πŸ’

𝒙 =βˆ’πŸ’πŸβˆ’πŸ’

𝒙 =πŸ’πŸπŸ’

3. 𝒙+πŸ—πŸπŸ

=βˆ’πŸπ’™βˆ’ 𝟏𝟐

πŸ‘

Sample student work:

𝒙 + πŸ—πŸπŸ

=βˆ’πŸπ’™ βˆ’ 𝟏

πŸπŸ‘

πŸπŸοΏ½βˆ’πŸπ’™ βˆ’πŸπŸοΏ½ = (𝒙 + πŸ—)πŸ‘

βˆ’πŸπŸ’π’™ βˆ’ πŸ” = πŸ‘π’™ + πŸπŸ• βˆ’πŸπŸ’π’™ + πŸπŸ’π’™ βˆ’ πŸ” = πŸ‘π’™ + πŸπŸ’π’™ + πŸπŸ•

βˆ’πŸ” = πŸπŸ•π’™ + πŸπŸ• βˆ’πŸ”βˆ’ πŸπŸ• = πŸπŸ•π’™ + πŸπŸ• βˆ’ πŸπŸ•

βˆ’πŸ‘πŸ‘ = πŸπŸ•π’™ βˆ’πŸ‘πŸ‘πŸπŸ•

=πŸπŸ‘πŸπŸ•

𝒙

βˆ’πŸπŸπŸ—

= 𝒙

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

4. πŸ–

πŸ‘βˆ’πŸ’π’™= πŸ“

πŸπ’™+πŸπŸ’

Sample student work: πŸ–

πŸ‘ βˆ’ πŸ’π’™=

πŸ“

πŸπ’™ + πŸπŸ’

πŸ–οΏ½πŸπ’™ +πŸπŸ’οΏ½ = (πŸ‘ βˆ’ πŸ’π’™)πŸ“

πŸπŸ”π’™ + 𝟐 = πŸπŸ“ βˆ’ πŸπŸŽπ’™ πŸπŸ”π’™ + 𝟐 βˆ’ 𝟐 = πŸπŸ“ βˆ’ 𝟐 βˆ’ πŸπŸŽπ’™

πŸπŸ”π’™ = πŸπŸ‘ βˆ’ πŸπŸŽπ’™ πŸπŸ”π’™ + πŸπŸŽπ’™ = πŸπŸ‘ βˆ’ πŸπŸŽπ’™ + πŸπŸŽπ’™

πŸ‘πŸ”π’™ = πŸπŸ‘ πŸ‘πŸ”πŸ‘πŸ”

𝒙 =πŸπŸ‘πŸ‘πŸ”

𝒙 =πŸπŸ‘πŸ‘πŸ”

Closing (5 minutes)

Summarize, or ask students to summarize, the main points from the lesson:

We know that proportions that have more than one term in the numerator and/or denominator can be solved the same way we normally solve a proportion.

When multiplying a fraction with more than one term in the numerator and/or denominator by a number, we should put the expressions with more than one term in parentheses, so we are less likely to forget to use the distributive property.

Exit Ticket (5 minutes)

𝒙 + πŸ’πŸπ’™ βˆ’ πŸ“

=πŸ‘πŸ“

πŸ“(𝒙 + πŸ’) = πŸ‘(πŸπ’™βˆ’ πŸ“)

Lesson Summary

Proportions are linear equations in disguise and are solved the same way we normally solve proportions.

When multiplying a fraction with more than one term in the numerator and/or denominator by a number, put the expressions with more than one term in parentheses so you remember to use the distributive property when transforming the equation. For example:

The equation πŸ“(𝒙+ πŸ’) = πŸ‘(πŸπ’™ βˆ’ πŸ“) is now clearly a linear equation and can be solved using the properties of equality.

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

Name Date

Lesson 8: Linear Equations in Disguise

Exit Ticket Solve the following equations for π‘₯.

1. 5π‘₯βˆ’83

=11π‘₯βˆ’95

2. π‘₯+117

=2π‘₯+1βˆ’8

3. βˆ’π‘₯βˆ’2βˆ’4

=3π‘₯+62

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

Exit Ticket Sample Solutions

1. πŸ“π’™βˆ’πŸ–πŸ‘

=πŸπŸπ’™βˆ’πŸ—πŸ“

πŸ“π’™ βˆ’ πŸ–πŸ‘

=πŸπŸπ’™ βˆ’ πŸ—

πŸ“

πŸ“(πŸ“π’™βˆ’ πŸ–) = πŸ‘(πŸπŸπ’™ βˆ’ πŸ—)

πŸπŸ“π’™ βˆ’ πŸ’πŸŽ = πŸ‘πŸ‘π’™ βˆ’ πŸπŸ•

πŸπŸ“π’™ βˆ’ πŸπŸ“π’™ βˆ’ πŸ’πŸŽ = πŸ‘πŸ‘π’™ βˆ’ πŸπŸ“π’™ βˆ’ πŸπŸ•

βˆ’πŸ’πŸŽ = πŸ–π’™ βˆ’ πŸπŸ•

βˆ’πŸ’πŸŽ+ πŸπŸ• = πŸ–π’™ βˆ’ πŸπŸ•+ πŸπŸ•

βˆ’πŸπŸ‘ = πŸ–π’™

βˆ’πŸπŸ‘πŸ–

= 𝒙

2. 𝒙+πŸπŸπŸ•

=πŸπ’™+πŸβˆ’πŸ–

𝒙 + πŸπŸπŸ•

=πŸπ’™ + πŸβˆ’πŸ–

πŸ•(πŸπ’™+ 𝟏) = βˆ’πŸ–(𝒙 + 𝟏𝟏) πŸπŸ’π’™ + πŸ• = βˆ’πŸ–π’™ βˆ’ πŸ–πŸ–

πŸπŸ’π’™ + πŸ• βˆ’ πŸ• = βˆ’πŸ–π’™ βˆ’ πŸ–πŸ– βˆ’ πŸ• πŸπŸ’π’™ = βˆ’πŸ–π’™ βˆ’ πŸ—πŸ“

πŸπŸ’π’™ + πŸ–π’™ = βˆ’πŸ–π’™ + πŸ–π’™ βˆ’ πŸ—πŸ“ πŸπŸπ’™ = βˆ’πŸ—πŸ“

𝒙 = βˆ’πŸ—πŸ“πŸπŸ

3. βˆ’π’™βˆ’πŸβˆ’πŸ’

=πŸ‘π’™+πŸ”πŸ

βˆ’π’™ βˆ’ πŸβˆ’πŸ’

=πŸ‘π’™ + πŸ”πŸ

βˆ’πŸ’(πŸ‘π’™ + πŸ”) = 𝟐(βˆ’π’™βˆ’ 𝟐)

βˆ’πŸπŸπ’™ βˆ’ πŸπŸ’ = βˆ’πŸπ’™ βˆ’ πŸ’ βˆ’πŸπŸπ’™ βˆ’ πŸπŸ’+ πŸπŸ’ = βˆ’πŸπ’™ βˆ’ πŸ’ + πŸπŸ’

βˆ’πŸπŸπ’™ = βˆ’πŸπ’™ + 𝟐𝟎 βˆ’πŸπŸπ’™ + πŸπ’™ = βˆ’πŸπ’™ + πŸπ’™ + 𝟐𝟎

βˆ’πŸπŸŽπ’™ = 𝟐𝟎 𝒙 = βˆ’πŸ

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

Problem Set Sample Solutions Students practice solving equations with rational expressions, if a solution possible.

Solve the following equations of rational expressions, if possible. If it cannot be solved, explain why.

1. πŸ“

πŸ”π’™βˆ’πŸ=

βˆ’πŸπ’™+𝟏

Sample student work:

πŸ“πŸ”π’™ βˆ’ 𝟐

=βˆ’πŸπ’™ + 𝟏

πŸ“(𝒙 + 𝟏) = βˆ’πŸ(πŸ”π’™βˆ’ 𝟐) πŸ“π’™ + πŸ“ = βˆ’πŸ”π’™ + 𝟐

πŸ“π’™ + πŸ“ βˆ’ πŸ“ = βˆ’πŸ”π’™ + 𝟐 βˆ’ πŸ“ πŸ“π’™ = βˆ’πŸ”π’™ βˆ’ πŸ‘

πŸ“π’™ + πŸ”π’™ = βˆ’πŸ”π’™ + πŸ”π’™ βˆ’ πŸ‘ πŸπŸπ’™ = βˆ’πŸ‘

𝒙 = βˆ’πŸ‘πŸπŸ

2. πŸ’βˆ’π’™πŸ–

=πŸ•π’™βˆ’πŸπŸ‘

Sample student work:

πŸ’ βˆ’ π’™πŸ–

=πŸ•π’™ βˆ’ πŸπŸ‘

πŸ–(πŸ•π’™βˆ’ 𝟏) = (πŸ’ βˆ’ 𝒙)πŸ‘ πŸ“πŸ”π’™ βˆ’ πŸ– = 𝟏𝟐 βˆ’ πŸ‘π’™

πŸ“πŸ”π’™ βˆ’ πŸ– + πŸ– = 𝟏𝟐 + πŸ– βˆ’ πŸ‘π’™ πŸ“πŸ”π’™ = 𝟐𝟎 βˆ’ πŸ‘π’™

πŸ“πŸ”π’™ + πŸ‘π’™ = 𝟐𝟎 βˆ’ πŸ‘π’™ + πŸ‘π’™ πŸ“πŸ—π’™ = 𝟐𝟎 πŸ“πŸ—πŸ“πŸ—

𝒙 =πŸπŸŽπŸ“πŸ—

𝒙 =πŸπŸŽπŸ“πŸ—

3. πŸ‘π’™π’™+𝟐

=πŸ“πŸ—

Sample student work:

πŸ‘π’™π’™ + 𝟐

=πŸ“πŸ—

πŸ—(πŸ‘π’™) = (𝒙 + 𝟐)πŸ“ πŸπŸ•π’™ = πŸ“π’™ + 𝟏𝟎

πŸπŸ•π’™ βˆ’ πŸ“π’™ = πŸ“π’™ βˆ’ πŸ“π’™ + 𝟏𝟎 πŸπŸπ’™ = 𝟏𝟎 𝟐𝟐𝟐𝟐

𝒙 =𝟏𝟎𝟐𝟐

𝒙 =πŸ“πŸπŸ

Lesson 8: Linear Equations in Disguise Date: 11/8/13

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

4. πŸπŸπ’™+πŸ”

πŸ‘=π’™βˆ’πŸ‘πŸ

Sample student work:

πŸπŸπ’™ + πŸ”

πŸ‘=𝒙 βˆ’ πŸ‘πŸ

πŸ‘(𝒙 βˆ’ πŸ‘) = πŸοΏ½πŸπŸπ’™ + πŸ”οΏ½

πŸ‘π’™ βˆ’ πŸ— = 𝒙 + 𝟏𝟐 πŸ‘π’™ βˆ’ πŸ— + πŸ— = 𝒙 + 𝟏𝟐 + πŸ—

πŸ‘π’™ = 𝒙 + 𝟐𝟏 πŸ‘π’™ βˆ’ 𝒙 = 𝒙 βˆ’ 𝒙 + 𝟐𝟏

πŸπ’™ = 𝟐𝟏

𝒙 =𝟐𝟏𝟐

5. πŸ•βˆ’πŸπ’™πŸ”

=π’™βˆ’πŸ“πŸ

Sample student work:

πŸ• βˆ’ πŸπ’™πŸ”

=𝒙 βˆ’ πŸ“πŸ

πŸ”(𝒙 βˆ’ πŸ“) = (πŸ• βˆ’ πŸπ’™)𝟏 πŸ”π’™ βˆ’ πŸ‘πŸŽ = πŸ• βˆ’ πŸπ’™

πŸ”π’™ βˆ’ πŸ‘πŸŽ + πŸ‘πŸŽ = πŸ• + πŸ‘πŸŽ βˆ’ πŸπ’™ πŸ”π’™ = πŸ‘πŸ• βˆ’ πŸπ’™

πŸ”π’™ + πŸπ’™ = πŸ‘πŸ• βˆ’ πŸπ’™ + πŸπ’™ πŸ–π’™ = πŸ‘πŸ• πŸ–πŸ–π’™ =

πŸ‘πŸ•πŸ–

𝒙 =πŸ‘πŸ•πŸ–

6. πŸπ’™+πŸ“πŸ

=πŸ‘π’™βˆ’πŸπŸ”

Sample student work:

πŸπ’™ + πŸ“πŸ

=πŸ‘π’™ βˆ’ πŸπŸ”

𝟐(πŸ‘π’™βˆ’ 𝟐) = πŸ”(πŸπ’™ + πŸ“) πŸ”π’™ βˆ’ πŸ’ = πŸπŸπ’™ + πŸ‘πŸŽ

πŸ”π’™ βˆ’ πŸ’ + πŸ’ = πŸπŸπ’™ + πŸ‘πŸŽ + πŸ’ πŸ”π’™ = πŸπŸπ’™ + πŸ‘πŸ’

πŸ”π’™ βˆ’ πŸπŸπ’™ = πŸπŸπ’™ βˆ’ πŸπŸπ’™ + πŸ‘πŸ’ βˆ’πŸ”π’™ = πŸ‘πŸ’

𝒙 = βˆ’πŸ‘πŸ’πŸ”

𝒙 = βˆ’πŸπŸ•πŸ‘

Lesson 8: Linear Equations in Disguise Date: 11/8/13

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

7. πŸ”π’™+πŸπŸ‘

=πŸ—βˆ’π’™πŸ•

Sample student work:

πŸ”π’™ + πŸπŸ‘

=πŸ— βˆ’ π’™πŸ•

(πŸ”π’™+ 𝟏)πŸ• = πŸ‘(πŸ— βˆ’ 𝒙) πŸ’πŸπ’™ + πŸ• = πŸπŸ• βˆ’ πŸ‘π’™

πŸ’πŸπ’™ + πŸ• βˆ’ πŸ• = πŸπŸ• βˆ’ πŸ• βˆ’ πŸ‘π’™ πŸ’πŸπ’™ = 𝟐𝟎 βˆ’ πŸ‘π’™

πŸ’πŸπ’™ + πŸ‘π’™ = 𝟐𝟎 βˆ’ πŸ‘π’™ + πŸ‘π’™ πŸ’πŸ“π’™ = 𝟐𝟎 πŸ’πŸ“πŸ’πŸ“

𝒙 =πŸπŸŽπŸ’πŸ“

𝒙 =πŸ’πŸ—

8. πŸπŸ‘π’™βˆ’πŸ–

𝟏𝟐=βˆ’πŸβˆ’π’™πŸπŸ“

Sample student work:

πŸπŸ‘π’™ βˆ’ πŸ–πŸπŸ

=βˆ’πŸβˆ’ π’™πŸπŸ“

𝟏𝟐(βˆ’πŸβˆ’ 𝒙) = οΏ½πŸπŸ‘π’™ βˆ’ πŸ–οΏ½πŸπŸ“

βˆ’πŸπŸ’ βˆ’ πŸπŸπ’™ = πŸ“π’™ βˆ’ 𝟏𝟐𝟎 βˆ’πŸπŸ’ βˆ’ πŸπŸπ’™ + πŸπŸπ’™ = πŸ“π’™ + πŸπŸπ’™ βˆ’ 𝟏𝟐𝟎

βˆ’πŸπŸ’ = πŸπŸ•π’™ βˆ’ 𝟏𝟐𝟎 βˆ’πŸπŸ’ + 𝟏𝟐𝟎 = πŸπŸ•π’™ βˆ’ 𝟏𝟐𝟎 + 𝟏𝟐𝟎

πŸ—πŸ” = πŸπŸ•π’™ πŸ—πŸ”πŸπŸ•

=πŸπŸ•πŸπŸ•

𝒙 πŸ—πŸ”πŸπŸ•

= 𝒙

9. πŸ‘βˆ’π’™πŸβˆ’π’™

=πŸ‘πŸ

Sample student work:

πŸ‘ βˆ’ π’™πŸ βˆ’ 𝒙

=πŸ‘πŸ

(πŸ‘ βˆ’ 𝒙)𝟐 = (𝟏 βˆ’ 𝒙)πŸ‘ πŸ” βˆ’ πŸπ’™ = πŸ‘ βˆ’ πŸ‘π’™

πŸ” βˆ’ πŸπ’™ + πŸπ’™ = πŸ‘ βˆ’ πŸ‘π’™ + πŸπ’™ πŸ” = πŸ‘ βˆ’ 𝒙

πŸ” βˆ’ πŸ‘ = πŸ‘ βˆ’ πŸ‘ βˆ’ 𝒙 πŸ‘ = βˆ’π’™

βˆ’πŸ‘ = 𝒙

Lesson 8: Linear Equations in Disguise Date: 11/8/13

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NYS COMMON CORE MATHEMATICS CURRICULUM 8β€’4 Lesson 8

10. In the diagram below, β–³ 𝑨𝑩π‘ͺ~ β–³ 𝑨′𝑩′π‘ͺβ€². Determine the lengths of 𝑨π‘ͺ and 𝑩π‘ͺ.

Sample student work:

𝒙 + πŸ’πŸ’.πŸ“

=πŸ‘π’™ βˆ’ πŸπŸ—

πŸ—(𝒙+ πŸ’) = πŸ’.πŸ“(πŸ‘π’™ βˆ’ 𝟐) πŸ—π’™ + πŸ‘πŸ” = πŸπŸ‘.πŸ“π’™ βˆ’ πŸ—

πŸ—π’™ + πŸ‘πŸ” + πŸ— = πŸπŸ‘.πŸ“π’™ βˆ’ πŸ—+ πŸ— πŸ—π’™ + πŸ’πŸ“ = πŸπŸ‘.πŸ“π’™

πŸ—π’™ βˆ’ πŸ—π’™ + πŸ’πŸ“ = πŸπŸ‘.πŸ“π’™ βˆ’ πŸ—π’™ πŸ’πŸ“ = πŸ’.πŸ“π’™ 𝟏𝟎 = 𝒙

The length of |𝑨π‘ͺ| = πŸπŸ’ π’„π’Ž and the length of |𝑩π‘ͺ| = πŸπŸ– π’„π’Ž.