College Algebra (11th Edition)

Published by Pearson
ISBN 10: 0321671791
ISBN 13: 978-0-32167-179-0

Chapter 1 - Review Exercises - Page 163: 23



Work Step by Step

Using $(a+b)(c+d)=ac+ad+bc+bd$ or the FOIL Method and using $i^2=-1$, the given expression $ (5-i)(3+4i) ,$ simplifies to \begin{array}{l}\require{cancel} 5(3)+5(4i)-i(3)-i(4i) \\\\= 15+20i-3i-4i^2 \\\\= 15+20i-3i-4(-1) \\\\= 15+20i-3i+4 \\\\= (15+4)+(20i-3i) \\\\= 19+17i .\end{array}
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