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Simplifying rational exponents

Simplify:

  1. 5(2x34)(3x15)
  2. (169)12

  1. 30x34x15Multiply the coefficients.30x34+15Use properties of exponents.30x1920Simplify.

  2. (916)12  Use definition of negative exponents.916  Rewrite as a radical.916  Use the quotient rule.34  Simplify.
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Simplify (8x)13(14x65).

28x2315

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Access these online resources for additional instruction and practice with radicals and rational exponents.

Key concepts

  • The principal square root of a number a is the nonnegative number that when multiplied by itself equals a. See [link] .
  • If a and b are nonnegative, the square root of the product ab is equal to the product of the square roots of a and b See [link] and [link] .
  • If a and b are nonnegative, the square root of the quotient ab is equal to the quotient of the square roots of a and b See [link] and [link] .
  • We can add and subtract radical expressions if they have the same radicand and the same index. See [link] and [link] .
  • Radical expressions written in simplest form do not contain a radical in the denominator. To eliminate the square root radical from the denominator, multiply both the numerator and the denominator by the conjugate of the denominator. See [link] and [link] .
  • The principal n th root of a is the number with the same sign as a that when raised to the n th power equals a. These roots have the same properties as square roots. See [link] .
  • Radicals can be rewritten as rational exponents and rational exponents can be rewritten as radicals. See [link] and [link] .
  • The properties of exponents apply to rational exponents. See [link] .

Section exercises

Verbal

What does it mean when a radical does not have an index? Is the expression equal to the radicand? Explain.

When there is no index, it is assumed to be 2 or the square root. The expression would only be equal to the radicand if the index were 1.

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Where would radicals come in the order of operations? Explain why.

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Every number will have two square roots. What is the principal square root?

The principal square root is the nonnegative root of the number.

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Can a radical with a negative radicand have a real square root? Why or why not?

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Numeric

For the following exercises, simplify each expression.

256

16

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256

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4(9+16)

10

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289121

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196

14

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1

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98

72

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2764

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815

955

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800

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169+144

25

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850

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18162

2

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192

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146624

26

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155+745

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150

56

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96100

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(42)(30)

635

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123475

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4225

215

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405324

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360361

61019

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51+3

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8117

1+172

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416

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3128+332

732

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5−32243

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15412545

155

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33−432+316

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Algebraic

For the following exercises, simplify each expression.

400x4

20x2

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4y2

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49p

7p

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(144p2q6)12

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m52289

17m2m

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93m2+27

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3ab2ba

2ba

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42n16n4

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225x349x

15x7

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344z+99z

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50y8

5y42

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490bc2

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3214d

47d7d

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q3263p

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813x

22+26x1−3x

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20121d4

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w3232w3250

w2w

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108x4+27x4

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12x2+23

3x3x2

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147k3

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125n10

5n55

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42q36q3

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81m361m2

9m19m

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72c22c

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144324d2

23d

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24 x 6 3 + 81 x 6 3

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162 x 6 16 x 4 4

3 2 x 2 4 2

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64 y 3

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128 z 3 3 −16 z 3 3

6 z 2 3

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1,024 c 10 5

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Real-world applications

A guy wire for a suspension bridge runs from the ground diagonally to the top of the closest pylon to make a triangle. We can use the Pythagorean Theorem to find the length of guy wire needed. The square of the distance between the wire on the ground and the pylon on the ground is 90,000 feet. The square of the height of the pylon is 160,000 feet. So the length of the guy wire can be found by evaluating 90,000 + 160,000 . What is the length of the guy wire?

500 feet

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A car accelerates at a rate of 6 4 t  m/s 2 where t is the time in seconds after the car moves from rest. Simplify the expression.

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Extensions

For the following exercises, simplify each expression.

8 16 4 2 2 1 2

−5 2 −6 7

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4 3 2 16 3 2 8 1 3

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m n 3 a 2 c −3 a −7 n −2 m 2 c 4

m n c a 9 c m n

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a a c

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x 64 y + 4 y 128 y

2 2 x + 2 4

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( 250 x 2 100 b 3 ) ( 7 b 125 x )

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64 3 + 256 4 64 + 256

3 3

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Practice Key Terms 6

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Source:  OpenStax, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
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