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 A60: 30

Answer

$-\dfrac{1}{2}+\dfrac{5}{2}i$

Work Step by Step

Multiply the numerator and the denominator by the conjugate of $1-i$ which is $1+i$. $\dfrac{2+3i}{1-i}=\dfrac{2+3i}{1-i}\cdot \dfrac{1+i}{1+i}$ Use FOIL method in the numerator and special formula $(a+b)(a-b)=a^2-b^2$ in the denominator. $=\dfrac{2(1)+2(i)+3i(1)+3i(i)}{1^2-i^2}$ $=\dfrac{2+2i+3i+3i^2}{1-i^2}$ Use $i^2=-1$. $=\dfrac{2+2i+3i+3(-1)}{1-(-1)}$ $=\dfrac{2+2i+3i-3}{1+1}$ Simplify. $=\dfrac{-1+5i}{2}$ $=-\dfrac{1}{2}+\dfrac{5}{2}i$ Hence, the solution in the standard form is $-\dfrac{1}{2}+\dfrac{5}{2}i$.
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