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Theorem nfdif 3122
Description: Bound-variable hypothesis builder for class difference. (Contributed by NM, 3-Dec-2003.) (Revised by Mario Carneiro, 13-Oct-2016.)
Hypotheses
Ref Expression
nfdif.1 𝑥𝐴
nfdif.2 𝑥𝐵
Assertion
Ref Expression
nfdif 𝑥(𝐴𝐵)

Proof of Theorem nfdif
Dummy variable 𝑦 is distinct from all other variables.
StepHypRef Expression
1 dfdif2 3008 . 2 (𝐴𝐵) = {𝑦𝐴 ∣ ¬ 𝑦𝐵}
2 nfdif.2 . . . . 5 𝑥𝐵
32nfcri 2223 . . . 4 𝑥 𝑦𝐵
43nfn 1594 . . 3 𝑥 ¬ 𝑦𝐵
5 nfdif.1 . . 3 𝑥𝐴
64, 5nfrabxy 2548 . 2 𝑥{𝑦𝐴 ∣ ¬ 𝑦𝐵}
71, 6nfcxfr 2226 1 𝑥(𝐴𝐵)
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wcel 1439  wnfc 2216  {crab 2364  cdif 2997
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 580  ax-in2 581  ax-io 666  ax-5 1382  ax-7 1383  ax-gen 1384  ax-ie1 1428  ax-ie2 1429  ax-8 1441  ax-10 1442  ax-11 1443  ax-i12 1444  ax-bndl 1445  ax-4 1446  ax-17 1465  ax-i9 1469  ax-ial 1473  ax-i5r 1474  ax-ext 2071
This theorem depends on definitions:  df-bi 116  df-tru 1293  df-fal 1296  df-nf 1396  df-sb 1694  df-clab 2076  df-cleq 2082  df-clel 2085  df-nfc 2218  df-rab 2369  df-dif 3002
This theorem is referenced by: (None)
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