Precalculus (6th Edition)

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

Chapter 9 - Systems and Matrices - 9.1 Systems of Linear Equations - 9.1 Exercises - Page 857: 34

Answer

$$\eqalign{ & {\text{Infinitely many solutions}}{\text{.}} \cr & \left( {\frac{{ - 5y - 2}}{3},y} \right) \cr} $$

Work Step by Step

$$\eqalign{ & 3x\,\, + \,\,\,\,5y\,\, = - 2\,\,\,\,\,\left( {\bf{1}} \right) \cr & 9x + \,\,15y\,\, = - 6\,\,\,\,\,\left( {\bf{2}} \right) \cr & {\text{Multiply the equation }}\left( {\bf{1}} \right){\text{ by }} - 3 \cr & - 9x - 15\,\,y\,\, = 6 \cr & \,\,\,\,9x + \,\,15y\,\, = - 6 \cr & {\text{Add both equations}} \cr & - 9x - 15\,\,y\,\, = 6 \cr & \underline {\,\,\,\,9x + \,\,15y\,\, = - 6} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,0 = 0\,\,\,\,\,\,\,\,\,\,\, \cr & {\text{The result}},{\text{ }}0 = 0,{\text{ is a true statement}},{\text{ which indicates that the }} \cr & {\text{equations are equivalent}}{\text{. Therefore,}} \cr & {\text{The system has infinitely many solutions}}{\text{.}} \cr & {\text{Solve the equation }}\left( {\bf{1}} \right){\text{ for }}x \cr & 3x\,\, + \,\,\,\,5y\,\, = - 2 \cr & x = \frac{{ - 5y - 2}}{3} \cr & \cr & {\text{The solutions of the system can be written in the form of a set }} \cr & {\text{of ordered pairs }}\left( {\frac{{ - 5y - 2}}{3},y} \right) \cr & \cr & {\text{Infinitely many solutions}}{\text{.}} \cr & \left( {\frac{{ - 5y - 2}}{3},y} \right) \cr} $$
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