## Elementary Algebra

Published by Cengage Learning

# Chapter 11 - Additional Topics - 11.4 - Complex Numbers - Problem Set 11.4: 12

#### Answer

$2i\sqrt 7$

#### Work Step by Step

The number $i$ is defined as $\sqrt {-1}$ We use the rules of multiplication for square roots to separate the radical: $\sqrt {-1}\sqrt {28}$ We subsititute in $i$ for $\sqrt {-1}$: $i\sqrt {28}$ We simplify the real square root using multiplication rules: $i\sqrt {4}\sqrt 7=2i\sqrt 7$

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