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: 38

Answer

(-1, 1, -1, 1)

Work Step by Step

The question asks to find the solution to the system of equations. Given: 1. $x + y + z + w = 0$ 2. $x + y + 2z + 2w = 0$ 3. $2x + 2y + 3z + 4w = 1$ 4. $2x + 3y + 4z + 5w = 2$ Subtract equation 1 from 2, equation 3 from 4 $x + y + 2z + 2w = 0$ -($x + y + z + w = 0$) $z + w = 0$ $2x + 3y + 4z + 5w = 2$ -($2x + 2y + 3z + 4w = 1$) $y + z + w = 1$ Since $z + w = 0$, then $y = 1$ Substitute y = 1 to all equations 1. $x + 1 + z + w = 0$ 2. $x + 1 + 2z + 2w = 0$ 3. $2x + 2 + 3z + 4w = 1$ 4. $2x + 3 + 4z + 5w = 2$ 1. $x + z + w = -1$ 2. $x + 2z + 2w = -1$ 3. $2x + 3z + 4w = -1$ 4. $2x + 4z + 5w = -1$ Multiply equation 2 by 2, then subtract it from equation 4 $2x + 4z + 5w = -1$ -($2x + 4z + 4w = -2$) $w = 1$ Since $z + w = 0$, then $z = -1$ Solve for x 1. $x + 1 + -1 + 1 = 0$ $x = -1$ Solution: (-1, 1, -1, 1)
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