Usage: 6 forms in 6 verses
Form Translated As     In Verse(s)
ησυνθετήσαμεν broke contract LXX.Ezra.10.2
ησυνθετήκατε have broken the contract LXX.Ezra.10.10
ησυνθέτησεν broke contract LXX.1Chr.2.7
ησυνθέτηκα I have broken contract LXX.Ps.73.15
ασυνθετήσητε should break contract LXX.Neh.1.8
ασυνθετήσαι to break contract LXX.Neh.13.27

Liddell-Scott-Jones

ἀσυνθετέω (asuntheteō) to break a contract G:V

ἀσυνθετέω-θετέω,

break covenant, be faithless, [LXX]; opposed to εὐσυνθετέω, [Refs 3rd c.BC+]

LSJ Scripture Refs: LXX.Ps.72.15*