I could invent you could invent he could invent we could invent you could invent they could invent
V-ing form
I could be inventing you could be inventing he could be inventing we could be inventing you could be inventing they could be inventing
Perfect
I could have invented you could have invented he could have invented we could have invented you could have invented they could have invented
V-ing perfect
I could have been inventing you could have been inventing he could have been inventing we could have been inventing you could have been inventing they could have been inventing
Negation
Simple form
I couldn't invent you couldn't invent he couldn't invent we couldn't invent you couldn't invent they couldn't invent
V-ing form
I couldn't be inventing you couldn't be inventing he couldn't be inventing we couldn't be inventing you couldn't be inventing they couldn't be inventing
Perfect
I couldn't have invented you couldn't have invented he couldn't have invented we couldn't have invented you couldn't have invented they couldn't have invented
V-ing perfect
I couldn't have been inventing you couldn't have been inventing he couldn't have been inventing we couldn't have been inventing you couldn't have been inventing they couldn't have been inventing
Interrogative form
Simple form
could I invent? could you invent? could he invent? could we invent? could you invent? could they invent?
V-ing form
could I be inventing? could you be inventing? could he be inventing? could we be inventing? could you be inventing? could they be inventing?
Perfect
could I have invented? could you have invented? could he have invented? could we have invented? could you have invented? could they have invented?
V-ing perfect
could I have been inventing? could you have been inventing? could he have been inventing? could we have been inventing? could you have been inventing? could they have been inventing?
Interro-negative form
Simple form
couldn't I invent? couldn't you invent? couldn't he invent? couldn't we invent? couldn't you invent? couldn't they invent?
V-ing form
couldn't I be inventing? couldn't you be inventing? couldn't he be inventing? couldn't we be inventing? couldn't you be inventing? couldn't they be inventing?
Perfect
couldn't I have invented? couldn't you have invented? couldn't he have invented? couldn't we have invented? couldn't you have invented? couldn't they have invented?
V-ing perfect
couldn't I have been inventing? couldn't you have been inventing? couldn't he have been inventing? couldn't we have been inventing? couldn't you have been inventing? couldn't they have been inventing?