Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 3 Linear Systems and Matrices - 3.7 Evaluate Determinants and Apply Cramer's Rule - 3.7 Exercises - Skill Practice - Page 208: 25

Answer

$A_{ABC}=21$

Work Step by Step

$A(-4,-4)$ $B(-1, 2)$ $C(2, -6)$ $A_{ABC}=\pm\frac{1}{2}\begin{vmatrix} -4 & -4 & 1\\ -1 & 2 & 1 \\ 2 & -6 & 1 \end{vmatrix}$ $=\pm\frac{1}{2}[-4(2+6)-(-4)(-1-2)+1(6-4)]$ $=\pm\frac{1}{2}(-32-12+2)$ $=\pm\frac{1}{2}.(-42)$ $=\pm21$ Hence $A_{ABC}=21$.
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