The English language often gives a word negative meaning by putting a few letters (called a prefix) in front of a word. For example, you are happy when you win but unhappy when you lose.
There are many prefixes that make a word negative, here are some:
Make a table. As you work with the textbook write in the adjectives that are negated in this way. Leave room for more prefixes in case you find them. Your table can look like this:
And so on.
As mentioned above, it is a good idea to keep a list of new words you learn. When doing this it is a good idea to also include a sample sentence to see how the word is used.