I'm trying to convert the decimal number -234 to hexadecimal and keep getting stuck. Here's what I'm doing:

1) Write 234 in binary: 1110 1010

2) Swap 0's and 1's: 0001 0101

3) Add 1: 0001 0110

But -2^4 + 2^2 + 2^1 = -10, not -234. So I get stuck before I can even try converting from binary to hex.

What am I doing wrong?