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: 59

Answer

$\{3-2i,3+2i\}$

Work Step by Step

The given equation has $a=1,b=-6$ and $c=13$. The discriminant is $=b^2-4ac$ $=(-6)^2-4(1)(13)$ $=36-52$ $=-16$ Use Quadratic formula. $x=\dfrac{-b\pm \sqrt {b^2-4ac}}{2a}$ Substitute the values of $a, b, c, $ and the discriminant. $x=\dfrac{-(-6)\pm \sqrt {-16}}{2(1)}$ Simplify. $x=\dfrac{6\pm \sqrt{16(-1)}}{2}$ $x=\dfrac{6\pm 4i}{2}$ Factor out $2$. $x=\dfrac{2(3\pm 2i)}{2}$ Cancel common factors. $x=3\pm 2i$ The equation has two solutions: $3-2i$ and $3+2i$. Check: For $x=3-2i$. $=(3-2i)^2-6(3-2i)+13$ $=9-12i+4i^2-18+12i+13$ $=4+4i^2$ $=4-4$ $=0$ For $x=3+2i$. $=(3+2i)^2-6(3+2i)+13$ $=9+12i+4i^2-18-12i+13$ $=4+4i^2$ $=4-4$ $=0$ Hence, the solution set is $\{3-2i,3+2i\}$.
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