Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Appendix A - Review - A.7 Complex Numbers; Quadratic Equations in the Complex Number System - A.7 Assess Your Understanding - Page A61: 61

Answer

$\{3-i,3+i\}$

Work Step by Step

The given equation is in standard form where $a=1,b=-6$ and $c=10$. The discriminant is $=b^2-4ac$ $=(-6)^2-4(1)(10)$ $=36-40$ $=-4$ Use Quadratic formula. $x=\dfrac{-b\pm \sqrt {b^2-4ac}}{2a}$ Substitute the values of $a, b, c, $ and the discriminant. $x=\dfrac{-(-6)\pm \sqrt {(-4)}}{2(1)}$ Simplify. $x=\dfrac{6\pm \sqrt{4(-1)}}{2}$ $x=\dfrac{6\pm 2i}{2}$ Factor out $2$. $x=\dfrac{2(3\pm i)}{2}$ Cancel the common factor $2$. $x=3\pm i$ The equation has two solutions: $3-i$ and $3+i$. Check: For $x=3-i$. $=(3-i)^2-6(3-i)+10$ $=9-6i+i^2-18+6i+10$ $=1+i^2$ $=1-1$ $=0$ For $x=3+i$. $=(3+i)^2-6(3+i)+10$ $=9+6i+i^2-18-6i+10$ $=1+i^2$ $=1-1$ $=0$ Hence, the solution set is $\{3-i,3+i\}$.
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