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Elementary Algebra

9.2 Simplify Square Roots

Elementary Algebra9.2 Simplify Square Roots
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Learning Objectives

By the end of this section, you will be able to:

  • Use the Product Property to simplify square roots
  • Use the Quotient Property to simplify square roots

Be Prepared 9.2

Before you get started take this readiness quiz.

  1. Simplify: 80176.
    If you missed this problem, review Example 1.65.
  2. Simplify: n9n3.
    If you missed this problem, review Example 6.59.
  3. Simplify: q4q12.
    If you missed this problem, review Example 6.60.

In the last section, we estimated the square root of a number between two consecutive whole numbers. We can say that 50 is between 7 and 8. This is fairly easy to do when the numbers are small enough that we can use Figure 9.2.

But what if we want to estimate 500? If we simplify the square root first, we’ll be able to estimate it easily. There are other reasons, too, to simplify square roots as you’ll see later in this chapter.

A square root is considered simplified if its radicand contains no perfect square factors.

Simplified Square Root

a is considered simplified if a has no perfect square factors.

So 31 is simplified. But 32 is not simplified, because 16 is a perfect square factor of 32.

Use the Product Property to Simplify Square Roots

The properties we will use to simplify expressions with square roots are similar to the properties of exponents. We know that (ab)m=ambm. The corresponding property of square roots says that ab=a·b.

Product Property of Square Roots

If a, b are non-negative real numbers, then ab=a·b.

We use the Product Property of Square Roots to remove all perfect square factors from a radical. We will show how to do this in Example 9.12.

Example 9.12

How To Use the Product Property to Simplify a Square Root

Simplify: 50.

Try It 9.23

Simplify: 48.

Try It 9.24

Simplify: 45.

Notice in the previous example that the simplified form of 50 is 52, which is the product of an integer and a square root. We always write the integer in front of the square root.

How To

Simplify a square root using the product property.

  1. Step 1. Find the largest perfect square factor of the radicand. Rewrite the radicand as a product using the perfect-square factor.
  2. Step 2. Use the product rule to rewrite the radical as the product of two radicals.
  3. Step 3. Simplify the square root of the perfect square.

Example 9.13

Simplify: 500.

Try It 9.25

Simplify: 288.

Try It 9.26

Simplify: 432.

We could use the simplified form 105 to estimate 500. We know 5 is between 2 and 3, and 500 is 105. So 500 is between 20 and 30.

The next example is much like the previous examples, but with variables.

Example 9.14

Simplify: x3.

Try It 9.27

Simplify: b5.

Try It 9.28

Simplify: p9.

We follow the same procedure when there is a coefficient in the radical, too.

Example 9.15

Simplify: 25y5.

Try It 9.29

Simplify: 16x7.

Try It 9.30

Simplify: 49v9.

In the next example both the constant and the variable have perfect square factors.

Example 9.16

Simplify: 72n7.

Try It 9.31

Simplify: 32y5.

Try It 9.32

Simplify: 75a9.

Example 9.17

Simplify: 63u3v5.

Try It 9.33

Simplify: 98a7b5.

Try It 9.34

Simplify: 180m9n11.

We have seen how to use the Order of Operations to simplify some expressions with radicals. To simplify 25+144 we must simplify each square root separately first, then add to get the sum of 17.

The expression 17+7 cannot be simplified—to begin we’d need to simplify each square root, but neither 17 nor 7 contains a perfect square factor.

In the next example, we have the sum of an integer and a square root. We simplify the square root but cannot add the resulting expression to the integer.

Example 9.18

Simplify: 3+32.

Try It 9.35

Simplify: 5+75.

Try It 9.36

Simplify: 2+98.

The next example includes a fraction with a radical in the numerator. Remember that in order to simplify a fraction you need a common factor in the numerator and denominator.

Example 9.19

Simplify: 4482.

Try It 9.37

Simplify: 10755.

Try It 9.38

Simplify: 6453.

Use the Quotient Property to Simplify Square Roots

Whenever you have to simplify a square root, the first step you should take is to determine whether the radicand is a perfect square. A perfect square fraction is a fraction in which both the numerator and the denominator are perfect squares.

Example 9.20

Simplify: 964.

Try It 9.39

Simplify: 2516.

Try It 9.40

Simplify: 4981.

If the numerator and denominator have any common factors, remove them. You may find a perfect square fraction!

Example 9.21

Simplify: 4580.

Try It 9.41

Simplify: 7548.

Try It 9.42

Simplify: 98162.

In the last example, our first step was to simplify the fraction under the radical by removing common factors. In the next example we will use the Quotient Property to simplify under the radical. We divide the like bases by subtracting their exponents, aman=amn,a0.

Example 9.22

Simplify: m6m4.

Try It 9.43

Simplify: a8a6.

Try It 9.44

Simplify: x14x10.

Example 9.23

Simplify: 48p73p3.

Try It 9.45

Simplify: 75x53x.

Try It 9.46

Simplify: 72z122z10.

Remember the Quotient to a Power Property? It said we could raise a fraction to a power by raising the numerator and denominator to the power separately.

(ab)m=ambm,b0

We can use a similar property to simplify a square root of a fraction. After removing all common factors from the numerator and denominator, if the fraction is not a perfect square we simplify the numerator and denominator separately.

Quotient Property of Square Roots

If a, b are non-negative real numbers and b0, then

ab=ab

Example 9.24

Simplify: 2164.

Try It 9.47

Simplify: 1949.

Try It 9.48

Simplify: 2881.

Example 9.25

How to Use the Quotient Property to Simplify a Square Root

Simplify: 27m3196.

Try It 9.49

Simplify: 24p349.

Try It 9.50

Simplify: 48x5100.

How To

Simplify a square root using the quotient property.

  1. Step 1. Simplify the fraction in the radicand, if possible.
  2. Step 2. Use the Quotient Property to rewrite the radical as the quotient of two radicals.
  3. Step 3. Simplify the radicals in the numerator and the denominator.

Example 9.26

Simplify: 45x5y4.

Try It 9.51

Simplify: 80m3n6.

Try It 9.52

Simplify: 54u7v8.

Be sure to simplify the fraction in the radicand first, if possible.

Example 9.27

Simplify: 81d925d4.

Try It 9.53

Simplify: 64x79x3.

Try It 9.54

Simplify: 16a9100a5.

Example 9.28

Simplify: 18p5q732pq2.

Try It 9.55

Simplify: 50x5y372x4y.

Try It 9.56

Simplify: 48m7n2125m5n9.

Section 9.2 Exercises

Practice Makes Perfect

Use the Product Property to Simplify Square Roots

In the following exercises, simplify.

53.

27

54.

80

55.

125

56.

96

57.

200

58.

147

59.

450

60.

252

61.

800

62.

288

63.

675

64.

1250

65.

x7

66.

y11

67.

p3

68.

q5

69.

m13

70.

n21

71.

r25

72.

s33

73.

49n17

74.

25m9

75.

81r15

76.

100s19

77.

98m5

78.

32n11

79.

125r13

80.

80s15

81.

200p13

82.

128q3

83.

242m23

84.

175n13

85.

147m7n11

86.

48m7n5

87.

75r13s9

88.

96r3s3

89.

300p9q11

90.

192q3r7

91.

242m13n21

92.

150m9n3

93.

5+12

94.

8+96

95.

1+45

96.

3+125

97.

10242

98.

8804

99.

3+903

100.

15+755

Use the Quotient Property to Simplify Square Roots

In the following exercises, simplify.

101.

4964

102.

10036

103.

12116

104.

144169

105.

7298

106.

7512

107.

45125

108.

300243

109.

x10x6

110.

p20p10

111.

y4y8

112.

q8q14

113.

200x72x3

114.

98y112y5

115.

96p96p

116.

108q103q2

117.

3635

118.

14465

119.

2081

120.

21196

121.

96x7121

122.

108y449

123.

300m564

124.

125n7169

125.

98r5100

126.

180s10144

127.

28q6225

128.

150r3256

129.

75r9s8

130.

72x5y6

131.

28p7q2

132.

45r3s10

133.

100x536x3

134.

49r1216r6

135.

121p581p2

136.

25r864r

137.

32x5y318x3y

138.

75r6s848rs4

139.

27p2q108p5q3

140.

50r5s2128r2s5

Everyday Math

141.
  1. Elliott decides to construct a square garden that will take up 288 square feet of his yard. Simplify 288 to determine the length and the width of his garden. Round to the nearest tenth of a foot.
  2. Suppose Elliott decides to reduce the size of his square garden so that he can create a 5-foot-wide walking path on the north and east sides of the garden. Simplify 2885 to determine the length and width of the new garden. Round to the nearest tenth of a foot.
142.
  1. Melissa accidentally drops a pair of sunglasses from the top of a roller coaster, 64 feet above the ground. Simplify 6416 to determine the number of seconds it takes for the sunglasses to reach the ground.
  2. Suppose the sunglasses in the previous example were dropped from a height of 144 feet. Simplify 14416 to determine the number of seconds it takes for the sunglasses to reach the ground.

Writing Exercises

143.

Explain why x4=x2. Then explain why x16=x8.

144.

Explain why 7+9 is not equal to 7+9.

Self Check

After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

This table has four columns and three rows. The columns are labeled, “I can…,” “confidently,” “with some help,” and “no—I don’t get it!” The rows under “I can…” Read, “use the Product Property to simplify square roots.,” and “use the Quotient Property to simplify square roots.” The other rows unders the other columns are blank.

After reviewing this checklist, what will you do to become confident for all objectives?

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