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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: be able to use the product property of square roots to multiply square roots.

Overview

  • The Product Property of Square Roots
  • Multiplication Rule for Square Root Expressions

The product property of square roots

In our work with simplifying square root expressions, we noted that

x y = x y

Since this is an equation, we may write it as

x y = x y

To multiply two square root expressions, we use the product property of square roots.

The product property x y = x y

x y = x y

The product of the square roots is the square root of the product.

In practice, it is usually easier to simplify the square root expressions before actually performing the multiplication. To see this, consider the following product:

8 48
We can multiply these square roots in either of two ways:

Simplify then multiply.

4 · 2 16 · 3 = ( 2 2 ) ( 4 3 ) = 2 · 4 2 · 3 = 8 6

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Multiply then simplify.

8 48 = 8 · 48 = 384 = 64 · 6 = 8 6

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Notice that in the second method, the expanded term (the third expression, 384 ) may be difficult to factor into a perfect square and some other number.

Multiplication rule for square root expressions

The preceding example suggests that the following rule for multiplying two square root expressions.

Rule for multiplying square root expressions

  1. Simplify each square root expression, if necessary.
  2. Perform the multiplecation.
  3. Simplify, if necessary.

Sample set a

Find each of the following products.

3 6 = 3 · 6 = 18 = 9 · 2 = 3 2

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8 2 = 2 2 2 = 2 2 · 2 = 2 4 = 2 · 2 = 4

This product might be easier if we were to multiply first and then simplify.

8 2 = 8 · 2 = 16 = 4

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20 7 = 4 5 7 = 2 5 · 7 = 2 35

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5 a 3 27 a 5 = ( a 5 a ) ( 3 a 2 3 a ) = 3 a 3 15 a 2 = 3 a 3 · a 15 = 3 a 4 15

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( x + 2 ) 7 x 1 = ( x + 2 ) 6 ( x + 2 ) x 1 = ( x + 2 ) 3 ( x + 2 ) x 1 = ( x + 2 ) 3 ( x + 2 ) ( x 1 ) or = ( x + 2 ) 3 x 2 + x 2

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Practice set a

Find each of the following products.

x + 4 x + 3

( x + 4 ) ( x + 3 )

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8 m 5 n 20 m 2 n

4 m 3 n 10 m

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9 ( k 6 ) 3 k 2 12 k + 36

3 ( k 6 ) 2 k 6

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2 a ( 5 a 8 a 3 )

a 10 4 a 2

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32 m 5 n 8 ( 2 m n 2 10 n 7 )

8 m 3 n 2 n 8 m 2 n 5 5 m

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Exercises

x + 2 x 3

( x + 2 ) ( x 3 )

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y + 3 y 2

( y + 3 ) ( y 2 )

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x + 9 ( x + 9 ) 2

( x + 9 ) x + 9

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3 a 2 15 a 3

3 a 2 5 a

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12 ( p q ) 3 3 ( p q ) 5

6 ( p q ) 4

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15 a 2 ( b + 4 ) 4 21 a 3 ( b + 4 ) 5

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125 m 5 n 4 r 8 8 m 6 r

10 m 5 n 2 r 4 10 m r

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7 ( 2 k 1 ) 11 ( k + 1 ) 3 14 ( 2 k 1 ) 10

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2 a 4 5 a 3 2 a 7

2 a 7 5

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2 m 3 n + 1 10 m n + 3

2 m 2 n + 2 5

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75 ( a 2 ) 7 48 a 96

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8 ( a 3 a )

2 2 a 2 6 a

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y ( y 5 + 3 y 3 )

y 2 ( y + 3 )

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8 a 5 ( 2 a 6 a 11 )

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12 m 3 ( 6 m 7 3 m )

6 m 2 ( m 3 2 1 )

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5 x 4 y 3 ( 8 x y 5 7 x )

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Exercises for review

( [link] ) Factor a 4 y 4 25 w 2 .

( a 2 y 2 + 5 w ) ( a 2 y 2 5 w )

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( [link] ) Find the slope of the line that passes through the points ( 5 , 4 ) and ( 3 , 4 ) .

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( [link] ) Perform the indicated operations:

15 x 2 20 x 6 x 2 + x 12 · 8 x + 12 x 2 2 x 15 ÷ 5 x 2 + 15 x x 2 25

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

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( [link] ) Simplify x 4 y 2 z 6 by removing the radical sign.

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( [link] ) Simplify 12 x 3 y 5 z 8 .

2 x y 2 z 4 3 x y

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Questions & Answers

how did you get 1640
Noor Reply
If auger is pair are the roots of equation x2+5x-3=0
Peter Reply
Wayne and Dennis like to ride the bike path from Riverside Park to the beach. Dennis’s speed is seven miles per hour faster than Wayne’s speed, so it takes Wayne 2 hours to ride to the beach while it takes Dennis 1.5 hours for the ride. Find the speed of both bikers.
MATTHEW Reply
420
Sharon
from theory: distance [miles] = speed [mph] × time [hours] info #1 speed_Dennis × 1.5 = speed_Wayne × 2 => speed_Wayne = 0.75 × speed_Dennis (i) info #2 speed_Dennis = speed_Wayne + 7 [mph] (ii) use (i) in (ii) => [...] speed_Dennis = 28 mph speed_Wayne = 21 mph
George
Let W be Wayne's speed in miles per hour and D be Dennis's speed in miles per hour. We know that W + 7 = D and W * 2 = D * 1.5. Substituting the first equation into the second: W * 2 = (W + 7) * 1.5 W * 2 = W * 1.5 + 7 * 1.5 0.5 * W = 7 * 1.5 W = 7 * 3 or 21 W is 21 D = W + 7 D = 21 + 7 D = 28
Salma
Devon is 32 32​​ years older than his son, Milan. The sum of both their ages is 54 54​. Using the variables d d​ and m m​ to represent the ages of Devon and Milan, respectively, write a system of equations to describe this situation. Enter the equations below, separated by a comma.
Aaron Reply
find product (-6m+6) ( 3m²+4m-3)
SIMRAN Reply
-42m²+60m-18
Salma
what is the solution
bill
how did you arrive at this answer?
bill
-24m+3+3mÁ^2
Susan
i really want to learn
Amira
I only got 42 the rest i don't know how to solve it. Please i need help from anyone to help me improve my solving mathematics please
Amira
Hw did u arrive to this answer.
Aphelele
hi
Bajemah
-6m(3mA²+4m-3)+6(3mA²+4m-3) =-18m²A²-24m²+18m+18mA²+24m-18 Rearrange like items -18m²A²-24m²+42m+18A²-18
Salma
complete the table of valuesfor each given equatio then graph. 1.x+2y=3
Jovelyn Reply
x=3-2y
Salma
y=x+3/2
Salma
Hi
Enock
given that (7x-5):(2+4x)=8:7find the value of x
Nandala
3x-12y=18
Kelvin
please why isn't that the 0is in ten thousand place
Grace Reply
please why is it that the 0is in the place of ten thousand
Grace
Send the example to me here and let me see
Stephen
A meditation garden is in the shape of a right triangle, with one leg 7 feet. The length of the hypotenuse is one more than the length of one of the other legs. Find the lengths of the hypotenuse and the other leg
Marry Reply
how far
Abubakar
cool u
Enock
state in which quadrant or on which axis each of the following angles given measure. in standard position would lie 89°
Abegail Reply
hello
BenJay
hi
Method
I am eliacin, I need your help in maths
Rood
how can I help
Sir
hmm can we speak here?
Amoon
however, may I ask you some questions about Algarba?
Amoon
hi
Enock
what the last part of the problem mean?
Roger
The Jones family took a 15 mile canoe ride down the Indian River in three hours. After lunch, the return trip back up the river took five hours. Find the rate, in mph, of the canoe in still water and the rate of the current.
cameron Reply
Shakir works at a computer store. His weekly pay will be either a fixed amount, $925, or $500 plus 12% of his total sales. How much should his total sales be for his variable pay option to exceed the fixed amount of $925.
mahnoor Reply
I'm guessing, but it's somewhere around $4335.00 I think
Lewis
12% of sales will need to exceed 925 - 500, or 425 to exceed fixed amount option. What amount of sales does that equal? 425 ÷ (12÷100) = 3541.67. So the answer is sales greater than 3541.67. Check: Sales = 3542 Commission 12%=425.04 Pay = 500 + 425.04 = 925.04. 925.04 > 925.00
Munster
difference between rational and irrational numbers
Arundhati Reply
When traveling to Great Britain, Bethany exchanged $602 US dollars into £515 British pounds. How many pounds did she receive for each US dollar?
Jakoiya Reply
how to reduced echelon form
Solomon Reply
Jazmine trained for 3 hours on Saturday. She ran 8 miles and then biked 24 miles. Her biking speed is 4 mph faster than her running speed. What is her running speed?
Zack Reply
d=r×t the equation would be 8/r+24/r+4=3 worked out
Sheirtina
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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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