For each of the following maps T : M2,2 -→ R, decide whether T is a linear transformation, and prove your answer.
(a) The determinant map T = det.(b) The trace map T = tr.(c) The map T sending a matrix A to the length of its first column vector.
(b) The trace map T = tr.
(c) The map T sending a matrix A to the length of its first column vector.