The four most popular methods for encoding (representing) negative binary numbers are known as “sign and magnitude”, “ones’ complement”, “two’s complement”, and “Excess-K”. There are alternative methods as well that aren’t as popular such as negative binary where the number base itself is actually negative (being negative 2).
That’s all there is to hexadecimal and octal. As you can see, hopefully, it’s not too complicated and is quite a bit like binary. Hexadecimal and octal were introduced to me when I was editing data files in a text editor that displayed the hexadecimal values of each byte as well. It was a pretty useful program.