could treble
Regular verb: treble - trebled- trebled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could treble
you could treble
he could treble
we could treble
you could treble
they could treble 	I could be trebling
you could be trebling
he could be trebling
we could be trebling
you could be trebling
they could be trebling	I could have trebled
you could have trebled
he could have trebled
we could have trebled
you could have trebled
they could have trebled	I could have been trebling
you could have been trebling
he could have been trebling
we could have been trebling
you could have been trebling
they could have been trebling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not treble
you could not treble
he could not treble
we could not treble
you could not treble
they could not treble 	I could not be trebling
you could not be trebling
he could not be trebling
we could not be trebling
you could not be trebling
they could not be trebling	I could not have trebled
you could not have trebled
he could not have trebled
we could not have trebled
you could not have trebled
they could not have trebled	I could not have been trebling
you could not have been trebling
he could not have been trebling
we could not have been trebling
you could not have been trebling
they could not have been trebling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I treble?
could you treble?
could he treble?
could we treble?
could you treble?
could they treble? 	could I be trebling?
could you be trebling?
could he be trebling?
could we be trebling?
could you be trebling?
could they be trebling? 	could I have trebled?
could you have trebled?
could he have trebled?
could we have trebled?
could you have trebled?
could they have trebled? 	could I have been trebling?
could you have been trebling?
could he have been trebling?
could we have been trebling?
could you have been trebling?
could they have been trebling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not treble?
could you not treble?
could he not treble?
could we not treble?
could you not treble?
could they not treble? 	could I not be trebling?
could you not be trebling?
could he not be trebling?
could we not be trebling?
could you not be trebling?
could they not be trebling? 	could I not have trebled?
could you not have trebled?
could he not have trebled?
could we not have trebled?
could you not have trebled?
could they not have trebled? 	could I not have been trebling?
could you not have been trebling?
could he not have been trebling?
could we not have been trebling?
could you not have been trebling?
could they not have been trebling?