can firm
Verbo regular: firm - firmed- firmed

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I can firm
you can firm
he can firm
we can firm
you can firm
they can firm 	I can be firming
you can be firming
he can be firming
we can be firming
you can be firming
they can be firming	I can have firmed
you can have firmed
he can have firmed
we can have firmed
you can have firmed
they can have firmed	I can have been firming
you can have been firming
he can have been firming
we can have been firming
you can have been firming
they can have been firming	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I cannot firm
you cannot firm
he cannot firm
we cannot firm
you cannot firm
they cannot firm 	I cannot be firming
you cannot be firming
he cannot be firming
we cannot be firming
you cannot be firming
they cannot be firming	I cannot have firmed
you cannot have firmed
he cannot have firmed
we cannot have firmed
you cannot have firmed
they cannot have firmed	I cannot have been firming
you cannot have been firming
he cannot have been firming
we cannot have been firming
you cannot have been firming
they cannot have been firming	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can I firm?
can you firm?
can he firm?
can we firm?
can you firm?
can they firm? 	can I be firming?
can you be firming?
can he be firming?
can we be firming?
can you be firming?
can they be firming? 	can I have firmed?
can you have firmed?
can he have firmed?
can we have firmed?
can you have firmed?
can they have firmed? 	can I have been firming?
can you have been firming?
can he have been firming?
can we have been firming?
can you have been firming?
can they have been firming? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can I not firm?
can you not firm?
can he not firm?
can we not firm?
can you not firm?
can they not firm? 	can I not be firming?
can you not be firming?
can he not be firming?
can we not be firming?
can you not be firming?
can they not be firming? 	can I not have firmed?
can you not have firmed?
can he not have firmed?
can we not have firmed?
can you not have firmed?
can they not have firmed? 	can I not have been firming?
can you not have been firming?
can he not have been firming?
can we not have been firming?
can you not have been firming?
can they not have been firming?