Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 1 - Section 1.6 - Complex Numbers - 1.6 Exercises - Page 64: 29


$(7-i)(4+2i)$ = $30+10i$

Work Step by Step

1. $(7-i)(4+2i)$ 2. Multiply the two binomials together (use the FOIL method and distribute the First, Outer, Inner, and Last terms): $28+14i-4i-2i^{2}$ 3. Combine like terms: $-2i^{2}+10i+28$ 4. Simplify $-2i^{2}$ to 2, because $i^{2}$ = -1, and $-2\times-1 = 2$: $2+10i+28$ 5. Combine like terms: $30+10i$
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