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I did use to live in London.
I did used to live in London.

Which one is correct?

According to the usage of emphatic do with past tense (eg "I lived in London/I did live in London"), did should change ‘used to’ to ‘use to,’ but I didn't find anything about it except in English Grammar Today by Cambridge. However, Cambridge used did with ‘used to.’ Shouldn't emphatic did change ‘used to’ to ‘use to’?

used to
From English Grammar Today

Emphatic did

We can use the emphatic auxiliary did with used to:

We never used to mix very much with the neighbours, but we did used to say hello to them in the street. (Don't use this form in written exams.)

Cambridge Dictionary

marked as duplicate by sumelic, marcellothearcane, David, Cascabel, Davo Jul 26 '17 at 11:07

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  • @sumelic looks to me like Mako212's flag, rather than the negation one... – marcellothearcane Jul 24 '17 at 18:38
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    @marcellothearcane: Well, the titles refer to different issues, but the answers both cover this topic. It could be marked as a duplicate of both. "I use to" is clearly a misspelling, while there is no consensus (at least not on this site, apparently) about the "correct" way to spell "I did use(d) to" or "I didn't use(d) to". – sumelic Jul 24 '17 at 18:40
  • Before asking this question, I had read your possible dubplicates. – user249253 Jul 24 '17 at 19:07
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    Can you edit your post to explain how your question is different? "Don't" is just the negative form of "do": I can't think of any syntactic difference between them that is relevant to this question. – sumelic Jul 24 '17 at 19:23
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    FWIW, I wouldn't put a 'did' in the past tense one - 'I used to...' – marcellothearcane Jul 24 '17 at 20:20