Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 2 - Section 2.1 - Complex Numbers - Exercise Set - Page 315: 51

Answer

The standard form of the expression $\left( 2-3i \right)\left( 1-i \right)-\left( 3-i \right)\left( 3+i \right)$ is $-11-5i$.

Work Step by Step

Consider the expression,$\left( 2-3i \right)\left( 1-i \right)-\left( 3-i \right)\left( 3+i \right)$ Use the FOIL method. $\begin{align} & \left( 2-3i \right)\left( 1-i \right)-\left( 3-i \right)\left( 3+i \right)=\left( 2-2i-3i+3{{i}^{2}} \right)-\left( 9+3i-3i-{{i}^{2}} \right) \\ & =\left( 2-5i+3{{i}^{2}} \right)-\left( 9-{{i}^{2}} \right) \end{align}$ Replace the value ${{i}^{2}}=-1$. $\begin{align} & \left( 2-3i \right)\left( 1-i \right)-\left( 3-i \right)\left( 3+i \right)=\left( 2-5i+3\left( -1 \right) \right)-\left( 9-\left( -1 \right) \right) \\ & =\left( 2-5i-3 \right)-\left( 9+1 \right) \\ & =-1-5i-10 \\ & =-11-5i \end{align}$ Therefore, the standard form of the expression $\left( 2-3i \right)\left( 1-i \right)-\left( 3-i \right)\left( 3+i \right)$ is $-11-5i$.
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