Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 10 - Systems of Equations and Inequalities - Section 10.1 Systems of Linear Equations: Substitution and Elimination - 10.1 Assess Your Understanding - Page 734: 42

Answer

$x=-3; y=2; z=1$ or, $(-3,2,1)$

Work Step by Step

We need to solve the given system of equations: $$2x+y=-4 ~~~(1)\\ -2y+4z=0 ~~~(2) \\ 3x-2z=-11 ~~~(3)$$ First, we will divide equation $(2)$ by $2$. $$-y+2z=0 ~~~(4)$$ Add equations $(3)$ and $(4)$ to eliminate $z$: $$3x-2z-y+2z=-11+0 \\ 3x-y=-11 ~~~(5)$$ Now, add equations $(1)$ and $(5) $to eliminate $x$: $$2x+y+3x-y=-4-11 \\ 5x= -15 \\ x=\dfrac{-15}{5}\\ x=-3$$ Now, back substitute the value of $x$ into Equation $(1)$ to solve for $y$: $$(2)(-3)+y=-4 \\ -6+y=-4 \\ y=-4+6 \\ y=2$$ Finally, back substitute the value of $y$ into Equation $(2)$ to solve for $z$: $$-2(2)+4z=0 \\-4+4z=0 \\ 4z=4 \\ z=1$$ So, the solution is: $x=-3; y=2; z=1$ or, $(-3,2,1)$
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