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Exercise 1

Avg difficulty 2.5

Given a column vector x=(x1x2),\mathbf x = \begin{pmatrix} x_1 \\ x_2 \end{pmatrix}, we define the transpose of x\mathbf x to be xT=(x1x2).\mathbf x^T = \begin{pmatrix} x_1 & x_2 \end{pmatrix}. If A=(3−20−1),x=(41),andy=(−23),A = \begin{pmatrix} 3 & -2 \\ 0 & -1 \end{pmatrix}, \mathbf x = \begin{pmatrix} 4 \\ 1 \end{pmatrix}, \quad \text{and} \quad \mathbf y = \begin{pmatrix} -2 \\ 3 \end{pmatrix}, find each of the following.

  1. AxA \mathbf x

  2. AyA \mathbf y

  3. xTy\mathbf x^T \mathbf y

  4. yTx\mathbf y^T \mathbf x

Judson, The ODE Project, §3.1 Linear Algebra in a Nutshell, Exercise 1

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Adapted from The ODE Project © 2019–2025 Thomas W. Judson. Licensed under CC BY 4.0. Source: The ODE Project. Imported at revision 7935458.