ταῦτα: is simply the proposition which Socrates makes, and the words ἀλλὰ ποιήσω ταῦτα is a formula of acceptance.
ἀλλά: well then, is often thus used in answers. After an imv., as here in Soph. El. 376 ff., ΗΛ. Φέρ᾽ εἰπὲ δὴ τὸ δεινόν . . . XP. ἀλλ᾽ ἐξερῶ τοι πᾶν ὅσον κάτοιδ̓ ἐγώ.
τίνα φῂς εἶναι: though assuming it as self-evident that rhetoric is a τέχνη, Polus is compelled, in commencing, to put his question quite generally. Socrates, in his answer, confines himself simply to deducing the consequences of Gorgias' admissions. The substitution of ἥντινα for τίνα is according to the strict rule, which, however, is not rigorously adhered to.
6 f.
ὡς . . . εἰρῆσθαι: cf. Rep. x. 595 b ὡς πρὸς ὑμᾶς εἰρῆσθαι. The active εἰπεῖν is more common. See Madv. 151; H. 956; GMT. 777. 2.
ὃ φῂς σὺ ποιῆσαι τέχνην: is to be explained according to 448 c πολλαὶ τέχναι ἐν ἀνθρώποις εἰσὶν ἐκ τῶν ἐμπειριῶν ἐμπείρως ηὑρημέναι, according to which an art arises from experience. Polus, however, has by this time forgotten his own words.
ἐν τῷ συγγράμματι: see on 448 c and Introd. § 14.