Math Help - Determine whether a Linear Transformation is Invertible

1. Determine whether a Linear Transformation is Invertible

Hey everyone, I have a final exam tomorrow and I would greatly appreciate it if someone could help me out with this question:

For each of the following linear transformations T, determine whether T is invertible and justify your answer.

1. T:R^2 -> R^3 defined by T(a_1, a_2) = (a_1 - 2a_2, a_2, 3a_1 + 4a_2).
2. T:R^3 -> R^3 defined by T(a_1, a_2) = (3a_1 - a_2, a_2, 4a_1).
3. T:M_2x2(R) -> M_2x2(R) defined by T(a b c d) = (a+b a c c+d).

Both of these are 2x2 square matrices so "a" corresponds to the (1,1) entry, "b" corresponds to the (1,2) entry, "c" corresponds to the (2,1) entry, and "d" corresponds to the (2,2) entry. Same with "a+b", "a", etc.

I think these deal with isomorphisms but I'm not sure. Also, there is a theorem that says T is invertible iff T is one-to-one and onto. But how do I prove that T is one-to-one and onto?

Thanks for you help. BTW, what happened to Latex?

2. I solved the first one which is not inversible.
A one to one function/transformation is also called injective, see
Injective function - Wikipedia, the free encyclopedia
Also, an onto function/transformatio is surjective function, seeSurjective function - Wikipedia, the free encyclopedia

Hope this helps!