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This module is from Elementary Algebra by Denny Burzynski and Wade Ellis, Jr. The distinction between the principal square root of the number x and the secondary square root of the number x is made by explanation and by example. The simplification of the radical expressions that both involve and do not involve fractions is shown in many detailed examples; this is followed by an explanation of how and why radicals are eliminated from the denominator of a radical expression. Real-life applications of radical equations have been included, such as problems involving daily output, daily sales, electronic resonance frequency, and kinetic energy.Objectives of this module: understand the process used in adding and subtracting square roots, be able to add and subtract square roots.

Overview

  • The Logic Behind The Process
  • The Process

The logic behind the process

Now we will study methods of simplifying radical expressions such as

4 3 + 8 3 or 5 2 x 11 2 x + 4 ( 2 x + 1 )

The procedure for adding and subtracting square root expressions will become apparent if we think back to the procedure we used for simplifying polynomial expressions such as

4 x + 8 x or 5 a 11 a + 4 ( a + 1 )

The variables x and a are letters representing some unknown quantities (perhaps x represents 3 and a represents 2 x ). Combining like terms gives us

4 x + 8 x = 12 x or 4 3 + 8 3 = 12 3 and 5 a - 11 a + 4 ( a + 1 ) or 5 2 x - 11 2 x + 4 ( 2 x + 1 ) 5 a - 11 a + 4 a + 4 5 2 x - 11 2 x + 4 2 x + 4 - 2 a + 4 - 2 2 x + 4

The process

Let’s consider the expression 4 3 + 8 3 . There are two ways to look at the simplification process:

  1. We are asking, “How many square roots of 3 do we have?”

    4 3 means we have 4 “square roots of 3”

    8 3 means we have 8 “square roots of 3”

    Thus, altogether we have 12 “square roots of 3.”
  2. We can also use the idea of combining like terms. If we recall, the process of combining like terms is based on the distributive property

    4 x + 8 x = 12 x because 4 x + 8 x = ( 4 + 8 ) x = 12 x

    We could simplify 4 3 + 8 3 using the distributive property.

    4 3 + 8 3 = ( 4 + 8 ) 3 = 12 3

Both methods will give us the same result. The first method is probably a bit quicker, but keep in mind, however, that the process works because it is based on one of the basic rules of algebra, the distributive property of real numbers.

Sample set a

Simplify the following radical expressions.

4 32 + 5 2 . Simplify 32 . 4 16 · 2 + 5 2 = 4 16 2 + 5 2 = 4 · 4 2 + 5 2 = 16 2 + 5 2 = 21 2

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- 3 x 75 + 2 x 48 - x 27 . Simple each of the three radicals . = - 3 x 25 · 3 + 2 x 16 · 3 - x 9 · 3 = - 15 x 3 + 8 x 3 - 3 x 3 = ( - 15 x + 8 x - 3 x ) 3 = - 10 x 3

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5 a 24 a 3 - 7 54 a 5 + a 2 6 a + 6 a . Simplify each radical . = 5 a 4 · 6 · a 2 · a - 7 9 · 6 · a 4 · a + a 2 6 a + 6 a = 10 a 2 6 a - 21 a 2 6 a + a 2 6 a + 6 a = ( 10 a 2 - 21 a 2 + a 2 ) 6 a + 6 a = - 10 a 2 6 a + 6 a Factor out - 2 a . (This step is optional .) = - 2 a ( 5 a 6 a - 3 )

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Practice set a

Find each sum or difference.

7 84 x 12 189 x + 2 21 x

48 21 x

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4 x 54 x 3 + 36 x 2 + 3 24 x 5 3 x

18 x 2 6 x + 3 x

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Sample set b

3 + 8 3 8 . We'll rationalize the denominator by multiplying this fraction by 1 in the form 3 + 8 3 + 8 . 3 + 8 3 8 · 3 + 8 3 + 8 = ( 3 + 8 ) ( 3 + 8 ) 3 2 ( 8 ) 2 = 9 + 3 8 + 3 8 + 8 8 9 8 = 9 + 6 8 + 8 1 = 17 + 6 8 = 17 + 6 4 · 2 = 17 + 12 2

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2 + 7 4 - 3 . Rationalize the denominator by multiplying this fraction by 1 in the from 4 + 3 4 + 3 . 2 + 7 4 - 3 · 4 + 3 4 + 3 = ( 2 + 7 ) ( 4 + 3 ) 4 2 - ( 3 ) 2 = 8 + 2 3 + 4 7 + 21 16 - 3 = 8 + 2 3 + 4 7 + 21 13

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Practice set b

Simplify each by performing the indicated operation.

5 ( 6 4 )

30 4 5

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( 5 + 7 ) ( 2 + 8 )

3 10 + 3 14

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( 3 2 2 3 ) ( 4 3 + 8 )

8 6 12

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4 + 5 3 8

12 + 8 2 + 3 5 + 2 10

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Exercises

For the following problems, simplify each expression by performing the indicated operation.

3 6 12 6

15 6

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6 40 + 8 80

12 10 + 32 5

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5 x y 2 x y 3 3 y 2 2 x 3 y

2 x y 2 2 x y

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24 2 54 4 12

4 6 8 3

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8 20 9 125 + 10 180

5

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14 + 2 56 3 136

5 14 6 34

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4 a x 3 x + 2 3 a 2 x 3 + 7 3 a 2 x 3

13 a x 3 x

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3 b y 5 y + 4 5 b 2 y 3 2 5 b 2 y 3

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( 1 + 3 ) ( 2 3 )

1 + 3

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( 3 2 ) ( 4 2 )

7 ( 2 2 )

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( 2 + 5 ) ( 2 + 3 5 )

17 + 4 10

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( 2 6 3 ) ( 3 6 + 2 3 )

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( 4 5 2 3 ) ( 3 5 + 3 )

54 2 15

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( 3 8 2 2 ) ( 4 2 5 8 )

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( 12 + 5 3 ) ( 2 3 2 12 )

42

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( 2 7 ) 2

11 4 7

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( 2 + 5 x ) 2

4 + 4 5 x + 5 x

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( 8 6 b ) 2

64 16 6 b + 6 b

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( 3 y 7 y ) 2

9 y 2 6 y 7 y + 7 y

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( 2 + 5 ) ( 2 5 )

1

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( 6 + 7 ) ( 6 7 )

29

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( x + y ) ( x y )

x y

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4 6 + 2

2 ( 6 2 ) 17

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4 + 5 4 5

21 + 8 5 11

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8 3 2 + 18

16 + 2 3 + 24 2 3 6 14

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2 b 3 b 3 b + 2 b

2 6 5

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Exercises for review

( [link] ) Simplify ( x 5 y 3 x 2 y ) 5 .

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( [link] ) Simplify ( 8 x 3 y ) 2 ( x 2 y 3 ) 4 .

64 x 14 y 14

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( [link] ) Write ( x 1 ) 4 ( x 1 ) 7 so that only positive exponents appear.

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( [link] ) Simplify 27 x 5 y 10 z 3 .

3 x 2 y 5 z 3 x z

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( [link] ) Simplify 1 2 + x by rationalizing the denominator.

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Questions & Answers

Ayele, K., 2003. Introductory Economics, 3rd ed., Addis Ababa.
Widad Reply
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Ariel
?
Ariel
What is economics
Widad Reply
the study of how humans make choices under conditions of scarcity
AI-Robot
U(x,y) = (x×y)1/2 find mu of x for y
Desalegn Reply
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Desalegn
what is ecnomics
Jan Reply
this is the study of how the society manages it's scarce resources
Belonwu
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John Reply
macroeconomic is the branch of economics which studies actions, scale, activities and behaviour of the aggregate economy as a whole.
husaini
etc
husaini
difference between firm and industry
husaini Reply
what's the difference between a firm and an industry
Abdul
firm is the unit which transform inputs to output where as industry contain combination of firms with similar production 😅😅
Abdulraufu
Suppose the demand function that a firm faces shifted from Qd  120 3P to Qd  90  3P and the supply function has shifted from QS  20  2P to QS 10  2P . a) Find the effect of this change on price and quantity. b) Which of the changes in demand and supply is higher?
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Jan
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Jan
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out-of-pocket costs for a firm, for example, payments for wages and salaries, rent, or materials
AI-Robot
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identify a demand and a supply curve
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Demand curve shows that how supply and others conditions affect on demand of a particular thing and what percent demand increase whith increase of supply of goods
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Source:  OpenStax, Elementary algebra. OpenStax CNX. May 08, 2009 Download for free at http://cnx.org/content/col10614/1.3
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