Need help with this linear algebra question

3. For each of the foitowing functions, determine if they are linear transformations. [1) T: R2 > IRE such that T = 2 (2) det : M2x2 - R such that det = ad - be, where M2x2 is the vector space of all 2 x 2 matrices. (3) tr : M2x2 - R such that tr = a + d, where M2x2 is the vector space of all 2 x 2 matrices. (4) T : M3x3 -> Max3 such that T space of all 3 x 3 matrices