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The number 50 is between what two whole numbers?

Since 7 2 = 49 , 49 = 7.

Since 8 2 = 64 , 64 = 8. Thus,

7 < 50 < 8

Thus, 50 is a number between 7 and 8.

A number line with arrows on each end, labeled at zero, seven and eight. Seven is also labeled as square root of forty-nine and eight is labeled as square root of sixty-four. There is a closed circle at square root of fifty and it is labeled as square root of fifty.

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Practice set b

Write the principal and secondary square roots of each number.

100

100 = 10 and 100 = 10

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121

121 = 11 and 121 = 11

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Use a calculator to obtain a decimal approximation for the two square roots of 35. Round to two decimal places.

5.92  and  5.92

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Meaningful expressions

Since we know that the square of any real number is a positive number or zero, we can see that expressions such as 16 do not describe real numbers. There is no real number that can be squared that will produce −16. For x to be a real number, we must have x 0. In our study of algebra, we will assume that all variables and all expressions in radicands represent nonnegative numbers (numbers greater than or equal to zero).

Sample set c

Write the proper restrictions that must be placed on the variable so that each expression represents a real number.

For x 3 to be a real number, we must have

x 3 0 or x 3

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For 2 m + 7 to be a real number, we must have

2 m + 7 0 or 2 m 7 or m 7 2

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Practice set c

Write the proper restrictions that must be placed on the variable so that each expression represents a real number.

Simplifying square roots

When variables occur in the radicand, we can often simplify the expression by removing the radical sign. We can do so by keeping in mind that the radicand is the square of some other expression. We can simplify a radical by seeking an expression whose square is the radicand. The following observations will help us find the square root of a variable quantity.

Since ( x 3 ) 2 = x 3 · 2 = x 6 , x 3 is a square root of x 6 . Also
Six divided by two is equal to three. There is an arrow pointing  towards six that is labeled as

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Since ( x 4 ) 2 = x 4 · 2 = x 8 , x 4 is a square root of x 8 . Also

Eight divided by two is equal to four. There is an arrow pointing  towards eight that is labeled as

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Since ( x 6 ) 2 = x 6 · 2 = x 12 , x 6 is a square root of x 12 . Also

Twelve divided by two is equal to six. There is an arrow pointing  towards twelve that is labeled as

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These examples suggest the following rule:

If a variable has an even exponent, its square root can be found by dividing that exponent by 2.

The examples of Sample Set B illustrate the use of this rule.

Sample set d

Simplify each expression by removing the radical sign. Assume each variable is nonnegative .

a 2 . We seek an expression whose square is  a 2 .  Since ( a ) 2 = a 2 , a 2 = a Notice that  2 ÷ 2 = 1.

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y 8 . We seek an expression whose square is  y 8 .  Since ( y 4 ) 2 = y 8 , y 8 = y 4 Notice that  8 ÷ 2 = 4.

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25 m 2 n 6 . We seek an expression whose square is  25 m 2 n 6 .  Since ( 5 m n 3 ) 2 = 25 m 2 n 6 , 25 m 2 n 6 = 5 m n 3 Notice that  2 ÷ 2 = 1  and  6 ÷ 2 = 3.

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121 a 10 ( b 1 ) 4 . We seek an expression whose square is  121 a 10 ( b 1 ) 4 . Since [ 11 a 5 ( b 1 ) 2 ] 2 = 121 a 10 ( b 1 ) 4 , 121 a 10 ( b 1 ) 4 = 11 a 5 ( b 1 ) 2 Then, 121 a 10 ( b 1 ) 4 = 11 a 5 ( b 1 ) 2 Notice that  10 ÷ 2 = 5  and  4 ÷ 2 = 2.

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Practice set d

Simplify each expression by removing the radical sign. Assume each variable is nonnegative.

100 x 8 y 12 z 2

10 x 4 y 6 z

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36 ( a + 5 ) 4

6 ( a + 5 ) 2

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225 w 4 ( z 2 1 ) 2

15 w 2 ( z 2 1 )

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0.25 y 6 z 14

0.5 y 3 z 7

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x 2 n , where n is a natural number.

x n

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x 4 n , where n is a natural number.

x 2 n

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Exercises

How many square roots does every positive real number have?

two

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The symbol represents which square root of a number?

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The symbol – represents which square root of a number?

secondary

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For the following problems, find the two square roots of the given number.

1 16

1 4 and 1 4

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25 36

5 6  and  5 6

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0.04

0.2 and 0.2

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1.21

1.1 and 1.1

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For the following problems, evaluate each expression. If the expression does not represent a real number, write "not a real number."

225

not a real number

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1

not a real number

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For the following problems, write the proper restrictions that must be placed on the variable so that the expression represents a real number.

2 x 8

x 4

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For the following problems, simplify each expression by removing the radical sign.

36 x 22 y 44

6 x 11 y 22

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169 w 4 z 6 ( m 1 ) 2

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25 x 12 ( y 1 ) 4

5 x 6 ( y 1 ) 2

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9 m 6 n 4 ( m + n ) 18

3 m 3 n 2 ( m + n ) 9

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( f 2 ) 2 ( g + 6 ) 4

( f 2 ) ( g + 6 ) 4

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( 2 c 3 ) 6 + ( 5 c + 1 ) 2

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64 r 4 s 22

8 r 2 s 11

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121 a 6 ( a 4 ) 8

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[ ( w + 6 ) 2 ]

w + 6

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[ 4 a 2 b 2 ( c 2 + 8 ) 2 ]

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1.21 h 4 k 4

1.1 h 2 k 2

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169 a 2 b 4 c 6 196 x 4 y 6 z 8

13 a b 2 c 3 14 x 2 y 3 z 4

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[ 81 y 4 ( z 1 ) 2 225 x 8 z 4 w 6 ]

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Exercised for review

( [link] ) Find the quotient. x 2 1 4 x 2 1 ÷ x 1 2 x + 1 .

x + 1 2 x 1

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( [link] ) Find the sum. 1 x + 1 + 3 x + 1 + 2 x 2 1 .

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( [link] ) Solve the equation, if possible: 1 x 2 = 3 x 2 x 2 3 x + 1 .

No solution ; x = 2 is excluded.

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( [link] ) Perform the division: 15 x 3 5 x 2 + 10 x 5 x .

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( [link] ) Perform the division: x 3 5 x 2 + 13 x 21 x 3 .

x 2 2 x + 7

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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.
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find product (-6m+6) ( 3m²+4m-3)
SIMRAN Reply
-42m²+60m-18
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bill
how did you arrive at this answer?
bill
-24m+3+3mÁ^2
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i really want to learn
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Hw did u arrive to this answer.
Aphelele
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Bajemah
-6m(3mA²+4m-3)+6(3mA²+4m-3) =-18m²A²-24m²+18m+18mA²+24m-18 Rearrange like items -18m²A²-24m²+42m+18A²-18
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x=3-2y
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y=x+3/2
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3x-12y=18
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please why isn't that the 0is in ten thousand place
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please why is it that the 0is in the place of ten thousand
Grace
Send the example to me here and let me see
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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
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cool u
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state in which quadrant or on which axis each of the following angles given measure. in standard position would lie 89°
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however, may I ask you some questions about Algarba?
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what the last part of the problem mean?
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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.
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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.
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I'm guessing, but it's somewhere around $4335.00 I think
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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
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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?
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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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