Find general invariant lines

5 The matrix \(\mathbf { M }\) is given by \(\mathbf { M } = \left( \begin{array} { r r } - \frac { 3 } { 5 } & \frac { 4 } { 5 } \\ \frac { 4 } { 5 } & \frac { 3 } { 5 } \end{array} \right)\).

1. The diagram in the Printed Answer Booklet shows the unit square \(O A B C\). The image of the unit square under the transformation represented by \(\mathbf { M }\) is \(O A ^ { \prime } B ^ { \prime } C ^ { \prime }\). Draw and clearly label \(O A ^ { \prime } B ^ { \prime } C ^ { \prime }\).
2. Find the equation of the line of invariant points of this transformation.
3. (a) Find the determinant of \(\mathbf { M }\).
   (b) Describe briefly how this value relates to the transformation represented by \(\mathbf { M }\).

1 A reflection is represented by the matrix \(\left[ \begin{array} { c c } 1 & 0 \\ 0 & - 1 \end{array} \right]\) State the equation of the line of invariant points. Circle your answer.
[0pt] [1 mark] $$x = 0 \quad y = 0 \quad y = x \quad y = - x$$

A transformation \(T: \mathbb{R}^2 \to \mathbb{R}^2\) is represented by the matrix $$\mathbf{A} = \begin{pmatrix} -4 & 2 \\ 2 & -1 \end{pmatrix}, \text{ where } k \text{ is a constant.}$$ Find the image under \(T\) of the line with equation \(y = 2x + 1\). [2]