Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 9 - Systems and Matrices - 9.3 Determinant Solution of Linear Systems - 9.3 Exercises - Page 886: 74

Answer

\[\left\{ {\left( { - 16,6} \right)} \right\}\]

Work Step by Step

\[\begin{gathered} \left\{ {\begin{array}{*{20}{c}} { - \frac{3}{4}x + \frac{2}{3}y = 16} \\ {\frac{5}{2}x + \frac{1}{2}y = - 37} \end{array}} \right. \hfill \\ {\text{Given the system}} \hfill \\ \left\{ {\begin{array}{*{20}{c}} {{a_1}x + {b_1}y = {c_1}} \\ {{a_2}x + {b_2}y = {c_2}} \end{array}} \right. \hfill \\ D = \left| {\begin{array}{*{20}{c}} {{a_1}}&{{b_1}} \\ {{a_2}}&{{b_2}} \end{array}} \right|,\,\,\,{D_x} = \left| {\begin{array}{*{20}{c}} {{c_1}}&{{b_1}} \\ {{c_2}}&{{b_2}} \end{array}} \right|,\,\,{D_y} = \left| {\begin{array}{*{20}{c}} {{a_1}}&{{c_1}} \\ {{a_2}}&{{c_2}} \end{array}} \right| \hfill \\ {\text{First find }}D,{\text{ If }}D \ne 0,\,{\text{ then find }}{D_x}{\text{ and }}{D_y} \hfill \\ D = \left| {\begin{array}{*{20}{c}} { - 3/4}&{2/3} \\ {5/2}&{1/2} \end{array}} \right| = - \frac{3}{8} - \frac{5}{3} = - \frac{{49}}{{24}} \hfill \\ {D_x} = \left| {\begin{array}{*{20}{c}} {16}&{2/3} \\ { - 37}&{1/2} \end{array}} \right| = 8 + \frac{{74}}{3} = \frac{{98}}{3} \hfill \\ {D_y} = \left| {\begin{array}{*{20}{c}} { - 3/4}&{16} \\ {5/2}&{ - 37} \end{array}} \right| = \frac{{111}}{4} - 40 = - \frac{{49}}{4} \hfill \\ {\text{Using the Cramer's rule}} \hfill \\ x = \frac{{{D_x}}}{D} = \frac{{98/3}}{{ - 49/24}} = - 16,\,\,\,\,\,\,\,\,\,y = \frac{{{D_y}}}{D} = \frac{{ - 49/4}}{{ - 49/24}} = 6 \hfill \\ {\text{The solution set is}} \hfill \\ \left\{ {\left( { - 16,6} \right)} \right\} \hfill \\ \end{gathered} \]
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