8) (10 points) If T is a linear transformation give its matrix representation with respect to the standard basis. If T is not a linear transformation explain why not.
1. T(a,b) = (a+b, a-2b, 3a-b)
2. T(a, b) = a + 4b
3. T(a, b) = 2ab
4. T(a,b) = (a+1, b-1)