can back
Verbo regular: back - backed- backed

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I can back
you can back
he can back
we can back
you can back
they can back 	I can be backing
you can be backing
he can be backing
we can be backing
you can be backing
they can be backing	I can have backed
you can have backed
he can have backed
we can have backed
you can have backed
they can have backed	I can have been backing
you can have been backing
he can have been backing
we can have been backing
you can have been backing
they can have been backing	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I can't back
you can't back
he can't back
we can't back
you can't back
they can't back 	I can't be backing
you can't be backing
he can't be backing
we can't be backing
you can't be backing
they can't be backing	I can't have backed
you can't have backed
he can't have backed
we can't have backed
you can't have backed
they can't have backed	I can't have been backing
you can't have been backing
he can't have been backing
we can't have been backing
you can't have been backing
they can't have been backing	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can I back?
can you back?
can he back?
can we back?
can you back?
can they back? 	can I be backing?
can you be backing?
can he be backing?
can we be backing?
can you be backing?
can they be backing? 	can I have backed?
can you have backed?
can he have backed?
can we have backed?
can you have backed?
can they have backed? 	can I have been backing?
can you have been backing?
can he have been backing?
can we have been backing?
can you have been backing?
can they have been backing? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can't I back?
can't you back?
can't he back?
can't we back?
can't you back?
can't they back? 	can't I be backing?
can't you be backing?
can't he be backing?
can't we be backing?
can't you be backing?
can't they be backing? 	can't I have backed?
can't you have backed?
can't he have backed?
can't we have backed?
can't you have backed?
can't they have backed? 	can't I have been backing?
can't you have been backing?
can't he have been backing?
can't we have been backing?
can't you have been backing?
can't they have been backing?