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 couldn't sum you couldn't sum he couldn't sum we couldn't sum you couldn't sum they couldn't sum	I couldn't be summing you couldn't be summing he couldn't be summing we couldn't be summing you couldn't be summing they couldn't be summing
Perfecto	Perfecto con V-ing
I couldn't have summed you couldn't have summed he couldn't have summed we couldn't have summed you couldn't have summed they couldn't have summed	I couldn't have been summing you couldn't have been summing he couldn't have been summing we couldn't have been summing you couldn't have been summing they couldn't 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
couldn't I sum? couldn't you sum? couldn't he sum? couldn't we sum? couldn't you sum? couldn't they sum?	couldn't I be summing? couldn't you be summing? couldn't he be summing? couldn't we be summing? couldn't you be summing? couldn't they be summing?
Perfecto	Perfecto con V-ing
couldn't I have summed? couldn't you have summed? couldn't he have summed? couldn't we have summed? couldn't you have summed? couldn't they have summed?	couldn't I have been summing? couldn't you have been summing? couldn't he have been summing? couldn't we have been summing? couldn't you have been summing? couldn't they have been summing?