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: 31

Answer

$x=-7,y=-5$

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: $D=5\cdot-5-1\cdot2=-25-2-27.$ Then applying Cramer's Rule: $x=\frac{\begin{vmatrix} -40 & 1\\ 11 & -5 \\ \end{vmatrix}}{5}=\frac{-40\cdot-5-1\cdot11}{-27}=\frac{189}{-27}=-7$ $y=\frac{\begin{vmatrix} 5 & -40 \\ 2 & 11 \\ \end{vmatrix}}{-27}=\frac{5\cdot11-(-40)\cdot2}{-27}=\frac{135}{-27}=-5$ Thus $x=-7,y=-5$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.