Solve the following recurrence relation in three ways

Hello again, this is a part of an exercise on Algorithms and Complexity.
Solve the following recurrence relation in three ways: (a) implementation of the central theorem
(b) using the recursion tree, and (c) the method of guess and inductive proof.

T(1) = 1
T(n) = 2T(n/4) + 3(n^2) for n > 1:

You may assume that n is a power of 4. Justify your answers.

i am going to post some answer i came out but with photo attachment because
i can't write here the answear :S

Here is my try with the method of the Recursion tree. Do you spot any mistakes?