Precalculus (6th Edition)

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

Chapter 9 - Systems and Matrices - 9.5 Nonlinear Systems of Equations - 9.5 Exercises - Page 904: 38

Answer

$$\left\{ {\left( {6,\frac{1}{{15}}} \right),\left( { - 1, - \frac{2}{5}} \right)} \right\}$$

Work Step by Step

$$\eqalign{ & \,\, - 5xy + 2 = 0\,\,\,\,\left( {\bf{1}} \right) \cr & \,\,\,\,\,\,x - 15y = 5\,\,\,\left( {\bf{2}} \right) \cr & \cr & {\text{Solve the equation }}\left( {\bf{1}} \right){\text{ for }}y \cr & - 5xy + 2 = 0 \cr & y = \frac{2}{{5x}} \cr & \cr & {\text{Substitute }}y = \frac{2}{{5x}}{\text{ for }}y{\text{ into the equation }}\left( {\bf{2}} \right) \cr & x - 15\left( {\frac{2}{{5x}}} \right) = 5 \cr & {\text{Solve for }}x \cr & x - \frac{6}{x} = 5 \cr & {x^2} - 6 = 5x \cr & {x^2} - 5x - 6 = 0 \cr & \left( {x - 6} \right)\left( {x + 1} \right) = 0 \cr & {x_1} = 6,\,\,\,\,{x_2} = - 1 \cr & \cr & {\text{Substitute }}{x_1} = 6{\text{ into the equation }}y = \frac{2}{{5x}} \cr & y = \frac{2}{{5\left( 6 \right)}} \cr & y = \frac{1}{{15}} \cr & {\text{The first solution is }}\left( {6,\frac{1}{{15}}} \right) \cr & \cr & {\text{Substitute }}{x_2} = - 1{\text{ into the equation }}y = \frac{2}{{5x}} \cr & y = \frac{2}{{5\left( { - 1} \right)}} \cr & y = - \frac{2}{5} \cr & {\text{The second solution is }}\left( { - 1, - \frac{2}{5}} \right) \cr & \cr & {\text{Therefore, the solution set of the system is}} \cr & \left\{ {\left( {6,\frac{1}{{15}}} \right),\left( { - 1, - \frac{2}{5}} \right)} \right\} \cr} $$
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