College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 6 - Section 6.4 - Determinants and Cramer's Rule - 6.4 Exercises - Page 535: 65

Answer

$x=\pm1$

Work Step by Step

We know that for a matrix $ \left[\begin{array}{rrr} a & b & c \\ d &e & f \\ g &h & i \\ \end{array} \right] $ the determinant is given as $D=a(ei-fh)-b(di-fg)+c(dh-eg).$ Thus, we have: $D=1(1\cdot 1-0\cdot0)-(0)(x^2\cdot 1-0\cdot x)+x(x^2\cdot 0-1\cdot x)=1(1)-0(x^2)+x(-x)=-x^2+1=-(x+1)(x-1)$. We know that this is equal to $0$, so $-(x+1)(x-1)=0$ Hence, $x=\pm1$
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