A First Course in Linear Algebra · Problem C16

Linear Transformations — Robert Beezer

Mathematics — Linear Algebra · matrix-representation-linear-transformation

Problem

Find the matrix representation of T:C3→C4T: \mathbb{C}^3 \to \mathbb{C}^4, T([xyz])=[3x+2y+zx+y+zx−3y2x+3y+z].T\left(\begin{bmatrix} x \\ y \\ z \end{bmatrix}\right) = \begin{bmatrix} 3x + 2y + z \\ x + y + z \\ x - 3y \\ 2x + 3y + z \end{bmatrix}.
Intuitive explanation

To find a matrix representation, you need to see how the transformation acts on the standard basis vectors of the domain. Apply TT to each of e1,e2,e3e_1, e_2, e_3 in C3\mathbb{C}^3—the outputs become the columns of your matrix. This works because any linear transformation is completely determined by where it sends basis vectors, and matrix multiplication distributes that action across coordinates.

Intuitive explanation

To find a matrix representation, you need to see how the transformation acts on the standard basis vectors of the domain. Apply TT to each of e1,e2,e3e_1, e_2, e_3 in C3\mathbb{C}^3—the outputs become the columns of your matrix. This works because any linear transformation is completely determined by where it sends basis vectors, and matrix multiplication distributes that action across coordinates.

Related theory

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