Herbert Weir Smyth, A Greek Grammar for Colleges

Thus, ““τοῦτο τὸ ψήφισμα ἐγένετο” this bill was passed” L. 13.56, ““ὃ δέδοικ᾽ ἐγὼ μὴ πάθηθ᾽ ὑ_μεῖς” which I fear lest you may suffer” D. 9.65, ἢν δ᾽ ἀποψηφίσωνται οἱ ἄλλοι, ἄπιμεν ἅπαντες τοὔμπαλιν but if the rest vote against (following), we shall all return back again X. A. 1.4.15, ““τὼ ξένω τώδε φίλω ἐστὸν ἐμώ” these two strangers are friends of mine” P. G. 487a.

a. The verbal predicate, when a copulative verb (917), may be attracted to the number of a predicate noun, which often stands between subject and verb: ““τὸ χωρίον τοῦτο, ὅπερ πρότερον Ἐννέα ὁδοὶ ἐκαλοῦντο” this place which was formerly called Nine Ways” T. 4.102, ““ἅπα_ν τὸ μέσον τῶν τειχῶν ἦσαν στάδιοι τρεῖς” the entire space between the walls was three stades” X. A. 1.4.4. So with the participles of such copulative verbs: τὴν ἡδονὴν διώκετε ὡς ἀγαθὸν ὄν (for οὖσαν) you chase after pleasure as if it were a good P. Pr. 354c.

WITH ONE SUBJECT

Subject in the Singular, Verb in the Plural