Answer
$5$
Work Step by Step
Multiply using the formula $(a_b)(a-b)=a^2-b^2$ to obtain:
$(2+i)(2-i)=2^2-i^2=4-i^2$
Since $i^2=-1$, the expression above simplifies to::
$=4 - (-1)\\
=4+1\\
=5$
Algebra 2 Common Core
by Hall, Prentice
Published by
Prentice Hall
ISBN 10:
0133186024
ISBN 13:
978-0-13318-602-4
Chapter 5 - Polynomials and Polynomial Functions - Cumulative Standards Review - Multiple Choice - Page 356: 17
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