Three \(n \times 1\) column vectors are denoted by \(\mathbf{x}_1\), \(\mathbf{x}_2\), \(\mathbf{x}_3\), and \(\mathbf{M}\) is an \(n \times n\) matrix. Show that if \(\mathbf{x}_1\), \(\mathbf{x}_2\), \(\mathbf{x}_3\) are linearly dependent then the vectors \(\mathbf{Mx}_1\), \(\mathbf{Mx}_2\), \(\mathbf{Mx}_3\) are also linearly dependent. [2]
The vectors \(\mathbf{y}_1\), \(\mathbf{y}_2\), \(\mathbf{y}_3\) and the matrix \(\mathbf{P}\) are defined as follows:
$$\mathbf{y}_1 = \begin{pmatrix} 1 \\ 5 \\ 7 \end{pmatrix}, \quad \mathbf{y}_2 = \begin{pmatrix} 2 \\ -3 \\ 4 \end{pmatrix}, \quad \mathbf{y}_3 = \begin{pmatrix} 5 \\ 51 \\ 55 \end{pmatrix},$$
$$\mathbf{P} = \begin{pmatrix} 1 & -4 & 3 \\ 0 & 2 & 5 \\ 0 & 0 & -7 \end{pmatrix}$$
- Show that \(\mathbf{y}_1\), \(\mathbf{y}_2\), \(\mathbf{y}_3\) are linearly dependent. [2]
- Find a basis for the linear space spanned by the vectors \(\mathbf{Py}_1\), \(\mathbf{Py}_2\), \(\mathbf{Py}_3\). [2]