1.
define a transformation $T : \mathbb{R}^3 \to \mathbb{R}^2 \text{ by } T(x) = Ax$ then
$let A = \begin{bmatrix} 1 & -5 & -7 \\ -3 & 7 & 5 \end{bmatrix},\ u = \begin{bmatrix} 1 \\ 2 \\ 3 \end{bmatrix},\ b = \begin{bmatrix} -2 \\ -2 \end{bmatrix},\ T(x) = Ax$
$a. \text{find } T(u)$
$b. \text{Find } x \in \mathbb{R}^3 \text{ whose image under } T \text{ is } b$
$c. \text{Is } x \text{ unique?}$
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