must factor
Regular verb: factor - factored- factored

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must factor
you must factor
he must factor
we must factor
you must factor
they must factor 	I must be factoring
you must be factoring
he must be factoring
we must be factoring
you must be factoring
they must be factoring	I must have factored
you must have factored
he must have factored
we must have factored
you must have factored
they must have factored	I must have been factoring
you must have been factoring
he must have been factoring
we must have been factoring
you must have been factoring
they must have been factoring	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't factor
you mustn't factor
he mustn't factor
we mustn't factor
you mustn't factor
they mustn't factor 	I mustn't be factoring
you mustn't be factoring
he mustn't be factoring
we mustn't be factoring
you mustn't be factoring
they mustn't be factoring	I mustn't have factored
you mustn't have factored
he mustn't have factored
we mustn't have factored
you mustn't have factored
they mustn't have factored	I mustn't have been factoring
you mustn't have been factoring
he mustn't have been factoring
we mustn't have been factoring
you mustn't have been factoring
they mustn't have been factoring	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I factor?
must you factor?
must he factor?
must we factor?
must you factor?
must they factor? 	must I be factoring?
must you be factoring?
must he be factoring?
must we be factoring?
must you be factoring?
must they be factoring? 	must I have factored?
must you have factored?
must he have factored?
must we have factored?
must you have factored?
must they have factored? 	must I have been factoring?
must you have been factoring?
must he have been factoring?
must we have been factoring?
must you have been factoring?
must they have been factoring? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I factor?
mustn't you factor?
mustn't he factor?
mustn't we factor?
mustn't you factor?
mustn't they factor? 	mustn't I be factoring?
mustn't you be factoring?
mustn't he be factoring?
mustn't we be factoring?
mustn't you be factoring?
mustn't they be factoring? 	mustn't I have factored?
mustn't you have factored?
mustn't he have factored?
mustn't we have factored?
mustn't you have factored?
mustn't they have factored? 	mustn't I have been factoring?
mustn't you have been factoring?
mustn't he have been factoring?
mustn't we have been factoring?
mustn't you have been factoring?
mustn't they have been factoring?