linearalgebra001 - Minus

There's the problem(s). I've already done the first two. My problem is with the third part(I think).

Since T(p(x)) = 1 + x + 2x^2 would I just do p(x) = T^(-1)(1 + x + 2x^2) to solve for p(x)? And if so, how exactly would I go about doing that?

Also, I think the first two parts are correct(I know the second part is correct if the first part is), but if they're not, please let me know.

Thanks in advance.