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Exercise 3

Avg difficulty 2.5

Suppose that AA is a 3×23\times2 matrix whose columns are v1\vvec_1 and v2\vvec_2; that is, A=[v1v2]A = \left[\begin{array}{rr} \vvec_1 & \vvec_2 \end{array} \right].

  1. What is the dimension of the vectors v1\vvec_1 and v2\vvec_2?

  2. What is the product A[10]A\twovec{1}{0} in terms of v1\vvec_1 and v2\vvec_2? What is the product A[01]A\twovec{0}{1}? What is the product A[23]A\twovec{2}{3}?

  3. If we know that A[10]=[3−21],   A[01]=[032],A\twovec{1}{0} = \threevec{3}{-2}{1},~~~ A\twovec{0}{1} = \threevec{0}{3}{2}, what is the matrix AA?

Austin, Understanding Linear Algebra, §2.2 Matrix multiplication and linear combinations, Exercise 3

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Adapted from Understanding Linear Algebra © 2023 David Austin. Licensed under CC BY 4.0. Source: Understanding Linear Algebra. Imported at revision 3e6dced.