Answer
$-3i$
Work Step by Step
Make the square roots positive by moving the $i$ out of the radical. Then combine like terms.
$\sqrt {-81}-\sqrt {-144}$
$i\sqrt {81}-i\sqrt {144}$
$9i-12i$
$-3i$
College Algebra (6th Edition)
by Blitzer, Robert F.
Published by
Pearson
ISBN 10:
0-32178-228-3
ISBN 13:
978-0-32178-228-1
Chapter 1 - Equations and Inequalities - Exercise Set 1.4 - Page 142: 30
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