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Simplify: 20 45 .

5

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Just like we use the Associative Property of Multiplication to simplify 5 ( 3 x ) and get 15 x , we can simplify 5 ( 3 x ) and get 15 x . We will use the Associative Property to do this in the next example.

Simplify: 5 18 2 8 .

Solution

5 18 2 8 Simplify the radicals. 5 · 9 · 2 2 · 4 · 2 5 · 3 · 2 2 · 2 · 2 15 2 4 2 Combine the like radicals. 11 2

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Simplify: 4 27 3 12 .

6 3

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Simplify: 3 20 7 45 .

−15 5

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Simplify: 3 4 192 5 6 108 .

Solution

3 4 192 5 6 108 Simplify the radicals. 3 4 64 · 3 5 6 36 · 3 3 4 · 8 · 3 5 6 · 6 · 3 6 3 5 3 Combine the like radicals. 3

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Simplify: 2 3 108 5 7 147 .

3

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Simplify: 3 5 200 3 4 128 .

0

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Simplify: 2 3 48 3 4 12 .

Solution

2 3 48 3 4 12 Simplify the radicals. 2 3 16 · 3 3 4 4 · 3 2 3 · 4 · 3 3 4 · 2 · 3 8 3 3 3 2 3 Find a common denominator to subtract the coefficients of the like radicals. 16 6 3 9 6 3 Simplify. 7 6 3

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Simplify: 2 5 32 1 3 8 .

14 15 2

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Simplify: 1 3 80 1 4 125 .

1 12 5

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In the next example, we will remove constant and variable factors from the square roots.

Simplify: 18 n 5 32 n 5 .

Solution

18 n 5 32 n 5 Simplify the radicals. 9 n 4 · 2 n 16 n 4 · 2 n 3 n 2 2 n 4 n 2 2 n Combine the like radicals. n 2 2 n

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Simplify: 32 m 7 50 m 7 .

m 3 2 m

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Simplify: 27 p 3 48 p 3 .

p 3 p

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Simplify: 9 50 m 2 6 48 m 2 .

Solution

9 50 m 2 6 48 m 2 Simplify the radicals. 9 25 m 2 · 2 6 16 m 2 · 3 9 · 5 m · 2 6 · 4 m · 3 45 m 2 24 m 3 The radicals are not like and so cannot be combined.

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Simplify: 5 32 x 2 3 48 x 2 .

20 x 2 12 x 3

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Simplify: 7 48 y 2 4 72 y 2 .

28 y 3 24 y 2

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Simplify: 2 8 x 2 5 x 32 + 5 18 x 2 .

Solution

2 8 x 2 5 x 32 + 5 18 x 2 Simplify the radicals. 2 4 x 2 · 2 5 x 16 · 2 + 5 9 x 2 · 2 2 · 2 x · 2 5 x · 4 · 2 + 5 · 3 x · 2 4 x 2 20 x 2 + 15 x 2 Combine the like radicals. x 2

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Simplify: 3 12 x 2 2 x 48 + 4 27 x 2 .

10 x 3

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Simplify: 3 18 x 2 6 x 32 + 2 50 x 2 .

−5 x 2

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Access this online resource for additional instruction and practice with the adding and subtracting square roots.

Key concepts

  • To add or subtract like square roots, add or subtract the coefficients and keep the like square root.
  • Sometimes when we have to add or subtract square roots that do not appear to have like radicals, we find like radicals after simplifying the square roots.

Practice makes perfect

Add and Subtract Like Square Roots

In the following exercises, simplify.

3 11 + 2 11 8 11

−3 11

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3 3 8 3 + 7 5

−5 3 + 7 5

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6 2 + 2 2 3 5

8 2 3 5

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3 2 a 4 2 a + 5 2 a

4 2 a

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11 b 5 11 b + 3 11 b

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8 3 c + 2 3 c 9 3 c

3 c

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3 5 d + 8 5 d 11 5 d

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5 3 a b + 3 a b 2 3 a b

4 3 a b

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8 11 c d + 5 11 c d 9 11 c d

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2 p q 5 p q + 4 p q

p q

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11 2 r s 9 2 r s + 3 2 r s

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Add and Subtract Square Roots that Need Simplification

In the following exercises, simplify.

1 4 98 1 3 128

3 4 2

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72 a 5 50 a 5

a 2 2 a

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80 c 7 20 c 7

2 c 3 5 c

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9 80 p 4 6 98 p 4

36 p 2 5 42 p 2 2

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2 50 r 8 + 4 54 r 8

10 r 4 2 + 12 r 4 6

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3 20 x 2 4 45 x 2 + 5 x 80

14 x 5

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2 28 x 2 63 x 2 + 6 x 7

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3 128 y 2 + 4 y 162 8 98 y 2

−12 y 2

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3 75 y 2 + 8 y 48 300 y 2

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Mixed Practice

175 k 4 63 k 4

−2 k 2 7

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8 13 4 13 3 13

13

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80 a 5 45 a 5

a 2 5 a

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4 24 x 2 54 x 2 + 3 x 6

8 x 6

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Everyday math

A decorator decides to use square tiles as an accent strip in the design of a new shower, but she wants to rotate the tiles to look like diamonds. She will use 9 large tiles that measure 8 inches on a side and 8 small tiles that measure 2 inches on a side. 9 ( 8 2 ) + 8 ( 2 2 ) . Determine the width of the accent strip by simplifying the expression 9 ( 8 2 ) + 8 ( 2 2 ) . (Round to the nearest tenth of an inch.)

124.5 inches

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Suzy wants to use square tiles on the border of a spa she is installing in her backyard. She will use large tiles that have area of 12 square inches, medium tiles that have area of 8 square inches, and small tiles that have area of 4 square inches. Once section of the border will require 4 large tiles, 8 medium tiles, and 10 small tiles to cover the width of the wall. Simplify the expression 4 12 + 8 8 + 10 4 to determine the width of the wall.

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Writing exercises

Explain the difference between like radicals and unlike radicals. Make sure your answer makes sense for radicals containing both numbers and variables.

Answers will vary.

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Explain the process for determining whether two radicals are like or unlike. Make sure your answer makes sense for radicals containing both numbers and variables.

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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!” Under the “I can…” column the rows read, “add and subtract like square roots.,” and “add and subtract square roots that need simplification.” The other rows under the other columns are empty.

What does this checklist tell you about your mastery of this section? What steps will you take to improve?

Practice Key Terms 1

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Source:  OpenStax, Elementary algebra. OpenStax CNX. Jan 18, 2017 Download for free at http://cnx.org/content/col12116/1.2
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