Linear Algebra and Its Applications (5th Edition)

Published by Pearson
ISBN 10: 032198238X
ISBN 13: 978-0-32198-238-4

Chapter 4 - Vector Spaces - 4.4 Exercises - Page 225: 29

Answer

The set of polynomials are linearly dependent.

Work Step by Step

Step 1: Write the coordinate vectors produced by the coordinate mapping of the set (solve eventual calculations) ${(1-t^2), t-2t^2+t^3, (1-t)^3}$ $\Leftrightarrow$ ${1-2t+t^2, t-2t^2+t^3, 1-3t+3t^2-t^3}$ that is (1 -2 1 0 ), (0 1 -2 1), (1 -3 3 -1) Step 2: Write the coordinate vectors as a column matrix and test for linear dependency (A$\mathbf{x}=\mathbf{0}$) \begin{bmatrix} 1 & 0 & 1 & 0 \\ -2 & 1 & -3 & 0 \\ 1 & -2 & 3 & 0 \\ 0 & 1 & 1 & 0 \end{bmatrix} $\Leftrightarrow$ \begin{bmatrix} 1 & 0 & 1 & 0 \\ 0 & 1 & -1 & 0 \\ 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 \end{bmatrix} $\implies$ The columns of the matrix are linearly dependent since there is a free variable (there is not a pivot position in every column). Hence the corresponding polynomials are also linearly dependent.
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