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: 33

Answer

$x=-t+3$ $y=2t-3$ $z=t$

Work Step by Step

Express x from the first equation. $x+y-z=0 \rightarrow x=-y+z$ $x+2y-3z=-3$ $2x+3y-4z=-3$ Substitute $ x=-y+z$ into the second and the third equation. $-y+z+2y-3z=-3$ $2(-y+z)+3y-4z=-3$ Simplify. $y-2z=-3$ $y-2z=-3$ Multiply the first equation by -1. $y-2z=-3 \rightarrow -y+2z=3$ Add these equations: $-y+2z=3$ $y-2z=-3$ $0=0 \rightarrow$ 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. $z=t$ $y-2z=-3 \rightarrow y=2t-3$ $x=-y+z \rightarrow x=-t+3$
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