Hey mate
Let's take things easy and in turns:
We have the structure of the major scale - C major for instance, ok?
C D E F G A B C and we give each note a number from 1 to 8
Now, in order to make a chord we add intervals to the root and play them simultaneously
C9 would be C E G Bb D and it's formula -> 1 3 5 b7 9 (it is a dominant 9th chord and we know that from the notation - it only has the 9th and no other signs) this means it's dominant.
First of all you must understand the basic structure of a triad - root, third, fifth - 1, 3 , 5 in the case of a major chord and 1, b3 (flat third or minor third), 5 in the case of a minor chord. The other intervals are being added and provide various qualities to the chord.
For instance, C maj = C E G and C minor = C Eb G
Here is your first assignment
Please write down the formulas of the D major, E major, F major, A major, B major G major as above and then their minor versions. Deal?
Cosmin