must impair
Regular verb: impair - impaired- impaired

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must impair
you must impair
he must impair
we must impair
you must impair
they must impair 	I must be impairing
you must be impairing
he must be impairing
we must be impairing
you must be impairing
they must be impairing	I must have impaired
you must have impaired
he must have impaired
we must have impaired
you must have impaired
they must have impaired	I must have been impairing
you must have been impairing
he must have been impairing
we must have been impairing
you must have been impairing
they must have been impairing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't impair
you mustn't impair
he mustn't impair
we mustn't impair
you mustn't impair
they mustn't impair 	I mustn't be impairing
you mustn't be impairing
he mustn't be impairing
we mustn't be impairing
you mustn't be impairing
they mustn't be impairing	I mustn't have impaired
you mustn't have impaired
he mustn't have impaired
we mustn't have impaired
you mustn't have impaired
they mustn't have impaired	I mustn't have been impairing
you mustn't have been impairing
he mustn't have been impairing
we mustn't have been impairing
you mustn't have been impairing
they mustn't have been impairing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I impair?
must you impair?
must he impair?
must we impair?
must you impair?
must they impair? 	must I be impairing?
must you be impairing?
must he be impairing?
must we be impairing?
must you be impairing?
must they be impairing? 	must I have impaired?
must you have impaired?
must he have impaired?
must we have impaired?
must you have impaired?
must they have impaired? 	must I have been impairing?
must you have been impairing?
must he have been impairing?
must we have been impairing?
must you have been impairing?
must they have been impairing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I impair?
mustn't you impair?
mustn't he impair?
mustn't we impair?
mustn't you impair?
mustn't they impair? 	mustn't I be impairing?
mustn't you be impairing?
mustn't he be impairing?
mustn't we be impairing?
mustn't you be impairing?
mustn't they be impairing? 	mustn't I have impaired?
mustn't you have impaired?
mustn't he have impaired?
mustn't we have impaired?
mustn't you have impaired?
mustn't they have impaired? 	mustn't I have been impairing?
mustn't you have been impairing?
mustn't he have been impairing?
mustn't we have been impairing?
mustn't you have been impairing?
mustn't they have been impairing?