The linear transformation T:M(2x2) --> P2 defined by

T[a b]

[c d] = a+2bx+(c+d)x^2

I have to prove that this is not invertible. I don't even know where to start because if I was trying to prove that it was invertible, I wouldn't be able to solve for the determinant since I don't know how I'm supposed to put the polynomial into a matrix since it seems to me that it would only have 3 entries. What should I do to show that this is not invertible?