could invent
Regular verb: invent - invented- invented

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could invent
you could invent
he could invent
we could invent
you could invent
they could invent 	I could be inventing
you could be inventing
he could be inventing
we could be inventing
you could be inventing
they could be inventing	I could have invented
you could have invented
he could have invented
we could have invented
you could have invented
they could have invented	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 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't invent
you couldn't invent
he couldn't invent
we couldn't invent
you couldn't invent
they couldn't invent 	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	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	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 	V-ing form 	Perfect 	V-ing perfect 	
could I invent?
could you invent?
could he invent?
could we invent?
could you invent?
could they invent? 	could I be inventing?
could you be inventing?
could he be inventing?
could we be inventing?
could you be inventing?
could they be inventing? 	could I have invented?
could you have invented?
could he have invented?
could we have invented?
could you have invented?
could they have invented? 	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 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I invent?
couldn't you invent?
couldn't he invent?
couldn't we invent?
couldn't you invent?
couldn't they invent? 	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? 	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? 	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?