Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 10 - Section 10.6 - Determinants and Cramer's Rule - 10.6 Exercises - Page 743: 41

Answer

$(-2,5)$

Work Step by Step

Step 1. Based on the Cramer’s Rule, we can define the determinants: $\begin{array}( \\|D|= \\ \\ \end{array} \begin{vmatrix} 2 &-1\\1 &2 \end{vmatrix}, \begin{array}( \\|D_x|= \\ \\ \end{array} \begin{vmatrix} -9 &-1\\8 &2 \end{vmatrix}, \begin{array}( \\|D_y|= \\ \\ \end{array} \begin{vmatrix} 2 &-9\\1&8 \end{vmatrix}$ Step 2. Evaluate the above determinants: $|D|=2\times2-(-1\times1)=5$, $|D_x|=-9\times2-(-1\times8)=-10$, $|D_y|=2\times(-8)-(-9\times1)=25$ Step 3. Find the solutions as: $x=\frac{|D_x|}{|D|}=-2$, $y=\frac{|D_y|}{|D|}=5$
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