Conjugación del verbo inglés
COULD SUM

Verbo regular: sum - summed - summed

Afirmación

Forma simple	Forma con V-ing
I could sum you could sum he could sum we could sum you could sum they could sum	I could be summing you could be summing he could be summing we could be summing you could be summing they could be summing
Perfecto	Perfecto con V-ing
I could have summed you could have summed he could have summed we could have summed you could have summed they could have summed	I could have been summing you could have been summing he could have been summing we could have been summing you could have been summing they could have been summing

Negación

Forma simple	Forma con V-ing
I could not sum you could not sum he could not sum we could not sum you could not sum they could not sum	I could not be summing you could not be summing he could not be summing we could not be summing you could not be summing they could not be summing
Perfecto	Perfecto con V-ing
I could not have summed you could not have summed he could not have summed we could not have summed you could not have summed they could not have summed	I could not have been summing you could not have been summing he could not have been summing we could not have been summing you could not have been summing they could not have been summing

Forma interrogativa

Forma simple	Forma con V-ing
could I sum? could you sum? could he sum? could we sum? could you sum? could they sum?	could I be summing? could you be summing? could he be summing? could we be summing? could you be summing? could they be summing?
Perfecto	Perfecto con V-ing
could I have summed? could you have summed? could he have summed? could we have summed? could you have summed? could they have summed?	could I have been summing? could you have been summing? could he have been summing? could we have been summing? could you have been summing? could they have been summing?

Forma interro-negativa

Forma simple	Forma con V-ing
could I not sum? could you not sum? could he not sum? could we not sum? could you not sum? could they not sum?	could I not be summing? could you not be summing? could he not be summing? could we not be summing? could you not be summing? could they not be summing?
Perfecto	Perfecto con V-ing
could I not have summed? could you not have summed? could he not have summed? could we not have summed? could you not have summed? could they not have summed?	could I not have been summing? could you not have been summing? could he not have been summing? could we not have been summing? could you not have been summing? could they not have been summing?