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: 30

Answer

$y=6,x=2$

Work Step by Step

We know that for a matrix \[ \left[\begin{array}{rr} a & b \\ c &d \\ \end{array} \right] \] the determinant, $D=ad-bc.$ Thus the determinant of the coefficient matrix: $D=2\cdot2-(-1)\cdot1=4+1=5.$ Then applying Cramer's Rule: $y=\frac{\begin{vmatrix} 2 & -2\\ 1 & 14 \\ \end{vmatrix}}{5}=\frac{2\cdot14-(-2)\cdot1}{5}=\frac{30}{5}=6$ $x=\frac{\begin{vmatrix} -2 & -1 \\ 14 & 2 \\ \end{vmatrix}}{5}=\frac{-2\cdot2-(-1)\cdot14}{5}=\frac{10}{5}=2$ Thus $y=6,x=2$
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