Precalculus (6th Edition) Blitzer

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

Chapter 2 - Review Exercises - Page 429: 3

Answer

The standard form of the expression $\left( 7-i \right)\left( 2+3i \right)$ is $17+19i$.

Work Step by Step

Consider the expression, $\left( 7-i \right)\left( 2+3i \right)$ Apply the FOIL method on the above expression Therefore, $\begin{align} & \left( 7-i \right)\left( 2+3i \right)=7\left( 2 \right)+7\left( 3i \right)-i\left( 2 \right)-i\left( 3i \right) \\ & =14+21i-2i-3{{i}^{2}} \end{align}$ As ${{i}^{2}}=-1$ So, $14+21i-2i-3{{i}^{2}}=14+21i-2i+3$ Combine the real part and imaginary part separately and either add or subtract as required. Therefore, $\begin{align} & 14+21i-2i+3=\left( 14+3 \right)+\left( 21i-2i \right) \\ & =17+\left( 21-2 \right)i \\ & =17+19i \end{align}$ Thus, $\left( 7-i \right)\left( 2+3i \right)=17+19i$ Hence, the standard form of the expression $\left( 7-i \right)\left( 2+3i \right)$ is $17+19i$.
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