Normally we agree that the sentence patterns "so...that" and "too...to" are interchangeable. For example,

1) The baby is so fat that its mother can't hold it. = 2) The baby is too fat for its mother to hold.

But I've googled and found that people also say:

3) The baby is SO fat for its mother TO HOLD.


4) The baby is SO fat for its mother TO HOLD IT.

Aren't sentences 3) and 4) wrong?

I would really appreciate your help.
3) and 4) are wrong. Yes. The Internet does not require all its contents to be filtered through a grammar committee, as you see!

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Thank you CJ,

Actually I searched the forum after I posted my question and found the following thread:

To + adverbs

Are these sentences correct:
1-The birds flew too fast to aim at.
2-These particles move too fast to detect.
3-He works too well to fire.
4-He works too well to complain about.

1a-The birds flew too fast to aim at them.
2a-These particles move too fast to detect them.
3a-He works too well to fire him.
4a-He works too well to complain about him.

I believe the last four sentences are not correct, but Miriam said that all of the 8 sentences were correct.

Are they?
I don't find the last four sentences to be correct.
I suppose you'll have to take your question up with Miriam if you need further details concerning her response, although I haven't seen her on the Forums for a really long time. Maybe it's the sort of structure that is permitted in Spanish, her native language. I really don't know.

I see. Thanks a lot, CJ. I guess I've been too dependent on the responses from the forum to make use of my own judgment.
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