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Theorem grpinveu 12948
Description: The left inverse element of a group is unique. Lemma 2.2.1(b) of [Herstein] p. 55. (Contributed by NM, 24-Aug-2011.)
Hypotheses
Ref Expression
grpinveu.b 𝐵 = (Base‘𝐺)
grpinveu.p + = (+g𝐺)
grpinveu.o 0 = (0g𝐺)
Assertion
Ref Expression
grpinveu ((𝐺 ∈ Grp ∧ 𝑋𝐵) → ∃!𝑦𝐵 (𝑦 + 𝑋) = 0 )
Distinct variable groups:   𝑦,𝐵   𝑦,𝐺   𝑦, +   𝑦, 0   𝑦,𝑋

Proof of Theorem grpinveu
Dummy variable 𝑧 is distinct from all other variables.
StepHypRef Expression
1 grpinveu.b . . . 4 𝐵 = (Base‘𝐺)
2 grpinveu.p . . . 4 + = (+g𝐺)
3 grpinveu.o . . . 4 0 = (0g𝐺)
41, 2, 3grpinvex 12921 . . 3 ((𝐺 ∈ Grp ∧ 𝑋𝐵) → ∃𝑦𝐵 (𝑦 + 𝑋) = 0 )
5 eqtr3 2209 . . . . . . . . . . . 12 (((𝑦 + 𝑋) = 0 ∧ (𝑧 + 𝑋) = 0 ) → (𝑦 + 𝑋) = (𝑧 + 𝑋))
61, 2grprcan 12947 . . . . . . . . . . . 12 ((𝐺 ∈ Grp ∧ (𝑦𝐵𝑧𝐵𝑋𝐵)) → ((𝑦 + 𝑋) = (𝑧 + 𝑋) ↔ 𝑦 = 𝑧))
75, 6imbitrid 154 . . . . . . . . . . 11 ((𝐺 ∈ Grp ∧ (𝑦𝐵𝑧𝐵𝑋𝐵)) → (((𝑦 + 𝑋) = 0 ∧ (𝑧 + 𝑋) = 0 ) → 𝑦 = 𝑧))
873exp2 1227 . . . . . . . . . 10 (𝐺 ∈ Grp → (𝑦𝐵 → (𝑧𝐵 → (𝑋𝐵 → (((𝑦 + 𝑋) = 0 ∧ (𝑧 + 𝑋) = 0 ) → 𝑦 = 𝑧)))))
98com24 87 . . . . . . . . 9 (𝐺 ∈ Grp → (𝑋𝐵 → (𝑧𝐵 → (𝑦𝐵 → (((𝑦 + 𝑋) = 0 ∧ (𝑧 + 𝑋) = 0 ) → 𝑦 = 𝑧)))))
109imp41 353 . . . . . . . 8 ((((𝐺 ∈ Grp ∧ 𝑋𝐵) ∧ 𝑧𝐵) ∧ 𝑦𝐵) → (((𝑦 + 𝑋) = 0 ∧ (𝑧 + 𝑋) = 0 ) → 𝑦 = 𝑧))
1110an32s 568 . . . . . . 7 ((((𝐺 ∈ Grp ∧ 𝑋𝐵) ∧ 𝑦𝐵) ∧ 𝑧𝐵) → (((𝑦 + 𝑋) = 0 ∧ (𝑧 + 𝑋) = 0 ) → 𝑦 = 𝑧))
1211expd 258 . . . . . 6 ((((𝐺 ∈ Grp ∧ 𝑋𝐵) ∧ 𝑦𝐵) ∧ 𝑧𝐵) → ((𝑦 + 𝑋) = 0 → ((𝑧 + 𝑋) = 0𝑦 = 𝑧)))
1312ralrimdva 2570 . . . . 5 (((𝐺 ∈ Grp ∧ 𝑋𝐵) ∧ 𝑦𝐵) → ((𝑦 + 𝑋) = 0 → ∀𝑧𝐵 ((𝑧 + 𝑋) = 0𝑦 = 𝑧)))
1413ancld 325 . . . 4 (((𝐺 ∈ Grp ∧ 𝑋𝐵) ∧ 𝑦𝐵) → ((𝑦 + 𝑋) = 0 → ((𝑦 + 𝑋) = 0 ∧ ∀𝑧𝐵 ((𝑧 + 𝑋) = 0𝑦 = 𝑧))))
1514reximdva 2592 . . 3 ((𝐺 ∈ Grp ∧ 𝑋𝐵) → (∃𝑦𝐵 (𝑦 + 𝑋) = 0 → ∃𝑦𝐵 ((𝑦 + 𝑋) = 0 ∧ ∀𝑧𝐵 ((𝑧 + 𝑋) = 0𝑦 = 𝑧))))
164, 15mpd 13 . 2 ((𝐺 ∈ Grp ∧ 𝑋𝐵) → ∃𝑦𝐵 ((𝑦 + 𝑋) = 0 ∧ ∀𝑧𝐵 ((𝑧 + 𝑋) = 0𝑦 = 𝑧)))
17 oveq1 5898 . . . 4 (𝑦 = 𝑧 → (𝑦 + 𝑋) = (𝑧 + 𝑋))
1817eqeq1d 2198 . . 3 (𝑦 = 𝑧 → ((𝑦 + 𝑋) = 0 ↔ (𝑧 + 𝑋) = 0 ))
1918reu8 2948 . 2 (∃!𝑦𝐵 (𝑦 + 𝑋) = 0 ↔ ∃𝑦𝐵 ((𝑦 + 𝑋) = 0 ∧ ∀𝑧𝐵 ((𝑧 + 𝑋) = 0𝑦 = 𝑧)))
2016, 19sylibr 134 1 ((𝐺 ∈ Grp ∧ 𝑋𝐵) → ∃!𝑦𝐵 (𝑦 + 𝑋) = 0 )
Colors of variables: wff set class
Syntax hints:  wi 4  wa 104  w3a 980   = wceq 1364  wcel 2160  wral 2468  wrex 2469  ∃!wreu 2470  cfv 5231  (class class class)co 5891  Basecbs 12480  +gcplusg 12555  0gc0g 12727  Grpcgrp 12911
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 710  ax-5 1458  ax-7 1459  ax-gen 1460  ax-ie1 1504  ax-ie2 1505  ax-8 1515  ax-10 1516  ax-11 1517  ax-i12 1518  ax-bndl 1520  ax-4 1521  ax-17 1537  ax-i9 1541  ax-ial 1545  ax-i5r 1546  ax-13 2162  ax-14 2163  ax-ext 2171  ax-sep 4136  ax-pow 4189  ax-pr 4224  ax-un 4448  ax-cnex 7920  ax-resscn 7921  ax-1re 7923  ax-addrcl 7926
This theorem depends on definitions:  df-bi 117  df-3an 982  df-tru 1367  df-nf 1472  df-sb 1774  df-eu 2041  df-mo 2042  df-clab 2176  df-cleq 2182  df-clel 2185  df-nfc 2321  df-ral 2473  df-rex 2474  df-reu 2475  df-rmo 2476  df-rab 2477  df-v 2754  df-sbc 2978  df-csb 3073  df-un 3148  df-in 3150  df-ss 3157  df-pw 3592  df-sn 3613  df-pr 3614  df-op 3616  df-uni 3825  df-int 3860  df-br 4019  df-opab 4080  df-mpt 4081  df-id 4308  df-xp 4647  df-rel 4648  df-cnv 4649  df-co 4650  df-dm 4651  df-rn 4652  df-res 4653  df-iota 5193  df-fun 5233  df-fn 5234  df-fv 5239  df-riota 5847  df-ov 5894  df-inn 8938  df-2 8996  df-ndx 12483  df-slot 12484  df-base 12486  df-plusg 12568  df-0g 12729  df-mgm 12798  df-sgrp 12831  df-mnd 12844  df-grp 12914
This theorem is referenced by:  grpinvf  12957  grplinv  12960  isgrpinv  12964
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