College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 1 - Section 1.3 - Complex Numbers; Quadratic Equations in the Complex Number System - 1.3 Assess Your Understanding - Page 112: 55



Work Step by Step

We know that $\sqrt{-1}=i$. Thus here: $x^2+4=0\\x^2=-4\\\sqrt{x^2}=\sqrt{-4}\\x=\pm\sqrt{-4}=\pm2\sqrt{-1}=\pm2i$
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