could back
Verbo regular: back - backed- backed

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

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could not back
you could not back
he could not back
we could not back
you could not back
they could not back 	I could not be backing
you could not be backing
he could not be backing
we could not be backing
you could not be backing
they could not be backing	I could not have backed
you could not have backed
he could not have backed
we could not have backed
you could not have backed
they could not have backed	I could not have been backing
you could not have been backing
he could not have been backing
we could not have been backing
you could not have been backing
they could not have been backing	

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

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