English verb conjugation
COULD FIRM

Regular verb: firm - firmed - firmed

Affirmation

Simple form	V-ing form
I could firm you could firm he could firm we could firm you could firm they could firm	I could be firming you could be firming he could be firming we could be firming you could be firming they could be firming
Perfect	V-ing perfect
I could have firmed you could have firmed he could have firmed we could have firmed you could have firmed they could have firmed	I could have been firming you could have been firming he could have been firming we could have been firming you could have been firming they could have been firming

Negation

Simple form	V-ing form
I could not firm you could not firm he could not firm we could not firm you could not firm they could not firm	I could not be firming you could not be firming he could not be firming we could not be firming you could not be firming they could not be firming
Perfect	V-ing perfect
I could not have firmed you could not have firmed he could not have firmed we could not have firmed you could not have firmed they could not have firmed	I could not have been firming you could not have been firming he could not have been firming we could not have been firming you could not have been firming they could not have been firming

Interrogative form

Simple form	V-ing form
could I firm? could you firm? could he firm? could we firm? could you firm? could they firm?	could I be firming? could you be firming? could he be firming? could we be firming? could you be firming? could they be firming?
Perfect	V-ing perfect
could I have firmed? could you have firmed? could he have firmed? could we have firmed? could you have firmed? could they have firmed?	could I have been firming? could you have been firming? could he have been firming? could we have been firming? could you have been firming? could they have been firming?

Interro-negative form

Simple form	V-ing form
could I not firm? could you not firm? could he not firm? could we not firm? could you not firm? could they not firm?	could I not be firming? could you not be firming? could he not be firming? could we not be firming? could you not be firming? could they not be firming?
Perfect	V-ing perfect
could I not have firmed? could you not have firmed? could he not have firmed? could we not have firmed? could you not have firmed? could they not have firmed?	could I not have been firming? could you not have been firming? could he not have been firming? could we not have been firming? could you not have been firming? could they not have been firming?