D chord inversions
D/F# and D/A are the first and second inversions of the D major. This means that the bass tone is shifting from D to F sharp or A. Both these chords are also referred to as slash chords.
D/F#
D/A
Try in a chord progression
G - D/F# - Em
D/A - Am - C
Theory of the D/F# and D/A chords
Both chords consist of the notes D, F#, A. The difference is that the order of notes shifts. F# is the bass note in the first inversion and A is the bass note in the second inversion.
A comparison between the main D major and the two inversions can be seen below.
Chord construction
D x - x - D - A - D - F#D/F# F# - A - D - A - D - F#
D/A x - A - D - A - D - F#
Guitar versions of the chord
Notes in chord
D D - F# - AD/F# F# - A - D
D/A A - D - F#
Only the order of notes differs