Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 10 - Section 10.2 - Systems of Linear Equations in Several Variables - 10.2 Exercises - Page 697: 35

Answer

$x=-2t+2 $ $ y=\frac{4}{3}t-\frac{2}{3} $ $z=t $; $t \in R $

Work Step by Step

Express x from the first equation. $x+3y-2z=0 \rightarrow x=-3y+2z$ $2x+4z=4$ $4x+6y=4$ Substitute $ x=-3y+2z$ into the second and the third equation. $2(-3y+2z)+4z=4$ $4(-3y+2z)+6y=4$ Simplify. $-6y+8z=4$ $-6y+8z=4$ Multiply the first equation by -1. $-6y+8z=4 \rightarrow 6y-8z=-4$ Add these equations: $6y-8z=-4$ $-6y+8z=4$ $0=0 \rightarrow$ This means that the system has infinitely many solutions, but x,y and z cannot be any random numbers. To describe the complete solution of the system, let $z=t$ where t is any real number. Use back-substitution to express x and y. $z=t$ $6y-8z=-4 \rightarrow 6y=8t-4 \rightarrow y=\frac{4}{3}t-\frac{2}{3} $ $x=-3y+2z \rightarrow x=-3(\frac{4}{3}t-\frac{2}{3})+2t \rightarrow x=-2t+2 $
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