The infinitive with and without "to"

[Jesus1]

Hello!. How are you?

Well, I found these two sentences yesterday
and, to be honest, I don?t know what is
the difference between the usage of
an infinitive with "to" and "without" to?

1.- All we have to do is SIGN a few documents...

2.- My plan is TO EXPLAIN...

Well, I would like to know if it?s possible
to use the infinitive with or without "to"
indistinctively in both sentences.
And... Could I do it as well in any sentence?

I mean...

Could I say: "All we have to do is TO SIGN..."

and... "My plan is EXPLAIN..." and be

grammatically correct?


Thanks a lot!

Jes?s

[DOlier]

[Tom]

[Jesus1]

Hello! Thanks a million for your replies.

But there?s Something I still don?t understand...

1.- All we have TO DO is SIGNING a few documents...

2.- My plan is EXPLAINING...

What if I choose "to do" instead of "doing"
as you said? Would the first sentence be right,
Dolier?

And the second one?

Thanks again!

Jes?s