What is correct Way of adding Negative Keywords ?
There are a number of similarities between how the match types react. As with your positive keywords, you can add negatives as broad, phrase and exact match. While matching behavior is largely similar with your negative types, there are a few key differences.
The biggest difference is that negative broad match won’t exclude queries that are synonyms or close variations of the negative keyword. It will only exclude queries that include all words within a keyword, irrespective of the order in which the words appear.
Read this link for examples and a better understanding: