Guitar chords in the key of G:
Chord G7-9 notes: G, B, F, Ab and B. You should not play the 1st string.
The string 2 (B) is left open.
G7-9 (G dominant 7th flat 9th) guitar chord's alternative names: G7b9, Gdom7b9, Gdom7-9.
1(G), 3(B), 5(D), b7(F), b9(G#/Ab).