Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 10 - Section 10.6 - Determinants and Cramer's Rule - 10.6 Exercises - Page 743: 28

Answer

92, Yes.

Work Step by Step

Evaluate the determinant with row4 cofactors: (use row4 or row 3 instead of row1 as they contains two zeros) $\begin{array}( \\|A|= \\ \\ \end{array} \begin{vmatrix} 1 & 2 &0&2\\3 &-4 &0&4\\0 &1 &6&0\\1 &0 &2&0 \end{vmatrix} \begin{array}( \\=(-1) \\ \\\end{array}\begin{vmatrix} 2 &0&2\\-4 &0&4\\1 &6&0 \end{vmatrix} \begin{array}( \\(-2) \\ \\\end{array}\begin{vmatrix} 1 &2&2\\3 &-4&4\\0 &1&0 \end{vmatrix}$ $|A|=(-1)(2(-24)+2(-24))-2((-1)(4-6))=96-4=92$ (here evaluate the 3x3 the best way you can.) As $|A|\ne0$, the matrix should have an inverse.
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