Negation of 8-bit hexadecimal I am looking for a mathematical formula / algorithm to find the negation of a 8-bit hexadecimal without having to expand into a binary form. 

E.g; 

0000BDDA -> 48602

FFFF4226 -> -48602

Need to get from 0000BDDA -> FFFF4226 without 2' complements / expanding it to binary.

I've been cracking my head at it but to no avail.

Any ideas?
Use the same formula as you do for two's complement. First, compute the complement of the number by complementing all letters. Then add 1. Complementing works using the following table:
$$
0 \leftrightarrow F, 1 \leftrightarrow E, 2 \leftrightarrow D, 3 \leftrightarrow C, 4 \leftrightarrow B, 5 \leftrightarrow A, 6 \leftrightarrow 9, 7 \leftrightarrow 8.
$$
Example: starting with 0000BDDA, we first get FFFF4225, and after adding 1, we get FFFF4226.

Why does this work? Exercise.