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Exercise 3

Avg difficulty 2.5

Consider the vectors v1=[21],v2=[−11],v3=[−20]\vvec_1 = \left[\begin{array}{r} 2 \\ 1 \end{array} \right], \vvec_2 = \left[\begin{array}{r} -1 \\ 1 \end{array} \right], \vvec_3 = \left[\begin{array}{r} -2 \\ 0 \end{array} \right]

  1. Find the linear combination with weights c1=2c_1 = 2, c2=−3c_2=-3, and c3=1c_3=1.

  2. Can you write the vector 0=[00]{\mathbf 0} = \left[\begin{array}{r} 0 \\ 0 \end{array}\right] as a linear combination of v1\vvec_1, v2\vvec_2, and v3\vvec_3? If so, describe all the ways in which you can do so.

  3. Can you write the vector 0=[00]{\mathbf 0} = \left[\begin{array}{r} 0 \\ 0 \end{array}\right] as a linear combination using just the first two vectors v1\vvec_1 v2\vvec_2? If so, describe all the ways in which you can do so.

  4. Can you write v3\vvec_3 as a linear combination of v1\vvec_1 and v2\vvec_2? If so, in how many ways?

Austin, Understanding Linear Algebra, §2.1 Vectors 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.