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Mirrors > Home > ILE Home > Th. List > 3dvdsdec | GIF version |
Description: A decimal number is divisible by three iff the sum of its two "digits" is divisible by three. The term "digits" in its narrow sense is only correct if 𝐴 and 𝐵 actually are digits (i.e. nonnegative integers less than 10). However, this theorem holds for arbitrary nonnegative integers 𝐴 and 𝐵, especially if 𝐴 is itself a decimal number, e.g. 𝐴 = ;𝐶𝐷. (Contributed by AV, 14-Jun-2021.) (Revised by AV, 8-Sep-2021.) |
Ref | Expression |
---|---|
3dvdsdec.a | ⊢ 𝐴 ∈ ℕ0 |
3dvdsdec.b | ⊢ 𝐵 ∈ ℕ0 |
Ref | Expression |
---|---|
3dvdsdec | ⊢ (3 ∥ ;𝐴𝐵 ↔ 3 ∥ (𝐴 + 𝐵)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | dfdec10 9153 | . . . 4 ⊢ ;𝐴𝐵 = ((;10 · 𝐴) + 𝐵) | |
2 | 9p1e10 9152 | . . . . . . . 8 ⊢ (9 + 1) = ;10 | |
3 | 2 | eqcomi 2121 | . . . . . . 7 ⊢ ;10 = (9 + 1) |
4 | 3 | oveq1i 5752 | . . . . . 6 ⊢ (;10 · 𝐴) = ((9 + 1) · 𝐴) |
5 | 9cn 8776 | . . . . . . 7 ⊢ 9 ∈ ℂ | |
6 | ax-1cn 7681 | . . . . . . 7 ⊢ 1 ∈ ℂ | |
7 | 3dvdsdec.a | . . . . . . . 8 ⊢ 𝐴 ∈ ℕ0 | |
8 | 7 | nn0cni 8957 | . . . . . . 7 ⊢ 𝐴 ∈ ℂ |
9 | 5, 6, 8 | adddiri 7745 | . . . . . 6 ⊢ ((9 + 1) · 𝐴) = ((9 · 𝐴) + (1 · 𝐴)) |
10 | 8 | mulid2i 7737 | . . . . . . 7 ⊢ (1 · 𝐴) = 𝐴 |
11 | 10 | oveq2i 5753 | . . . . . 6 ⊢ ((9 · 𝐴) + (1 · 𝐴)) = ((9 · 𝐴) + 𝐴) |
12 | 4, 9, 11 | 3eqtri 2142 | . . . . 5 ⊢ (;10 · 𝐴) = ((9 · 𝐴) + 𝐴) |
13 | 12 | oveq1i 5752 | . . . 4 ⊢ ((;10 · 𝐴) + 𝐵) = (((9 · 𝐴) + 𝐴) + 𝐵) |
14 | 5, 8 | mulcli 7739 | . . . . 5 ⊢ (9 · 𝐴) ∈ ℂ |
15 | 3dvdsdec.b | . . . . . 6 ⊢ 𝐵 ∈ ℕ0 | |
16 | 15 | nn0cni 8957 | . . . . 5 ⊢ 𝐵 ∈ ℂ |
17 | 14, 8, 16 | addassi 7742 | . . . 4 ⊢ (((9 · 𝐴) + 𝐴) + 𝐵) = ((9 · 𝐴) + (𝐴 + 𝐵)) |
18 | 1, 13, 17 | 3eqtri 2142 | . . 3 ⊢ ;𝐴𝐵 = ((9 · 𝐴) + (𝐴 + 𝐵)) |
19 | 18 | breq2i 3907 | . 2 ⊢ (3 ∥ ;𝐴𝐵 ↔ 3 ∥ ((9 · 𝐴) + (𝐴 + 𝐵))) |
20 | 3z 9051 | . . 3 ⊢ 3 ∈ ℤ | |
21 | 7 | nn0zi 9044 | . . . 4 ⊢ 𝐴 ∈ ℤ |
22 | 15 | nn0zi 9044 | . . . 4 ⊢ 𝐵 ∈ ℤ |
23 | zaddcl 9062 | . . . 4 ⊢ ((𝐴 ∈ ℤ ∧ 𝐵 ∈ ℤ) → (𝐴 + 𝐵) ∈ ℤ) | |
24 | 21, 22, 23 | mp2an 422 | . . 3 ⊢ (𝐴 + 𝐵) ∈ ℤ |
25 | 9nn 8856 | . . . . . 6 ⊢ 9 ∈ ℕ | |
26 | 25 | nnzi 9043 | . . . . 5 ⊢ 9 ∈ ℤ |
27 | zmulcl 9075 | . . . . 5 ⊢ ((9 ∈ ℤ ∧ 𝐴 ∈ ℤ) → (9 · 𝐴) ∈ ℤ) | |
28 | 26, 21, 27 | mp2an 422 | . . . 4 ⊢ (9 · 𝐴) ∈ ℤ |
29 | zmulcl 9075 | . . . . . . 7 ⊢ ((3 ∈ ℤ ∧ 𝐴 ∈ ℤ) → (3 · 𝐴) ∈ ℤ) | |
30 | 20, 21, 29 | mp2an 422 | . . . . . 6 ⊢ (3 · 𝐴) ∈ ℤ |
31 | dvdsmul1 11442 | . . . . . 6 ⊢ ((3 ∈ ℤ ∧ (3 · 𝐴) ∈ ℤ) → 3 ∥ (3 · (3 · 𝐴))) | |
32 | 20, 30, 31 | mp2an 422 | . . . . 5 ⊢ 3 ∥ (3 · (3 · 𝐴)) |
33 | 3t3e9 8845 | . . . . . . . 8 ⊢ (3 · 3) = 9 | |
34 | 33 | eqcomi 2121 | . . . . . . 7 ⊢ 9 = (3 · 3) |
35 | 34 | oveq1i 5752 | . . . . . 6 ⊢ (9 · 𝐴) = ((3 · 3) · 𝐴) |
36 | 3cn 8763 | . . . . . . 7 ⊢ 3 ∈ ℂ | |
37 | 36, 36, 8 | mulassi 7743 | . . . . . 6 ⊢ ((3 · 3) · 𝐴) = (3 · (3 · 𝐴)) |
38 | 35, 37 | eqtri 2138 | . . . . 5 ⊢ (9 · 𝐴) = (3 · (3 · 𝐴)) |
39 | 32, 38 | breqtrri 3925 | . . . 4 ⊢ 3 ∥ (9 · 𝐴) |
40 | 28, 39 | pm3.2i 270 | . . 3 ⊢ ((9 · 𝐴) ∈ ℤ ∧ 3 ∥ (9 · 𝐴)) |
41 | dvdsadd2b 11467 | . . 3 ⊢ ((3 ∈ ℤ ∧ (𝐴 + 𝐵) ∈ ℤ ∧ ((9 · 𝐴) ∈ ℤ ∧ 3 ∥ (9 · 𝐴))) → (3 ∥ (𝐴 + 𝐵) ↔ 3 ∥ ((9 · 𝐴) + (𝐴 + 𝐵)))) | |
42 | 20, 24, 40, 41 | mp3an 1300 | . 2 ⊢ (3 ∥ (𝐴 + 𝐵) ↔ 3 ∥ ((9 · 𝐴) + (𝐴 + 𝐵))) |
43 | 19, 42 | bitr4i 186 | 1 ⊢ (3 ∥ ;𝐴𝐵 ↔ 3 ∥ (𝐴 + 𝐵)) |
Colors of variables: wff set class |
Syntax hints: ∧ wa 103 ↔ wb 104 ∈ wcel 1465 class class class wbr 3899 (class class class)co 5742 0cc0 7588 1c1 7589 + caddc 7591 · cmul 7593 3c3 8740 9c9 8746 ℕ0cn0 8945 ℤcz 9022 ;cdc 9150 ∥ cdvds 11420 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 588 ax-in2 589 ax-io 683 ax-5 1408 ax-7 1409 ax-gen 1410 ax-ie1 1454 ax-ie2 1455 ax-8 1467 ax-10 1468 ax-11 1469 ax-i12 1470 ax-bndl 1471 ax-4 1472 ax-13 1476 ax-14 1477 ax-17 1491 ax-i9 1495 ax-ial 1499 ax-i5r 1500 ax-ext 2099 ax-sep 4016 ax-pow 4068 ax-pr 4101 ax-un 4325 ax-setind 4422 ax-cnex 7679 ax-resscn 7680 ax-1cn 7681 ax-1re 7682 ax-icn 7683 ax-addcl 7684 ax-addrcl 7685 ax-mulcl 7686 ax-mulrcl 7687 ax-addcom 7688 ax-mulcom 7689 ax-addass 7690 ax-mulass 7691 ax-distr 7692 ax-i2m1 7693 ax-0lt1 7694 ax-1rid 7695 ax-0id 7696 ax-rnegex 7697 ax-cnre 7699 ax-pre-ltirr 7700 ax-pre-ltwlin 7701 ax-pre-lttrn 7702 ax-pre-ltadd 7704 |
This theorem depends on definitions: df-bi 116 df-3or 948 df-3an 949 df-tru 1319 df-fal 1322 df-nf 1422 df-sb 1721 df-eu 1980 df-mo 1981 df-clab 2104 df-cleq 2110 df-clel 2113 df-nfc 2247 df-ne 2286 df-nel 2381 df-ral 2398 df-rex 2399 df-reu 2400 df-rab 2402 df-v 2662 df-sbc 2883 df-dif 3043 df-un 3045 df-in 3047 df-ss 3054 df-pw 3482 df-sn 3503 df-pr 3504 df-op 3506 df-uni 3707 df-int 3742 df-br 3900 df-opab 3960 df-id 4185 df-xp 4515 df-rel 4516 df-cnv 4517 df-co 4518 df-dm 4519 df-iota 5058 df-fun 5095 df-fv 5101 df-riota 5698 df-ov 5745 df-oprab 5746 df-mpo 5747 df-pnf 7770 df-mnf 7771 df-xr 7772 df-ltxr 7773 df-le 7774 df-sub 7903 df-neg 7904 df-inn 8689 df-2 8747 df-3 8748 df-4 8749 df-5 8750 df-6 8751 df-7 8752 df-8 8753 df-9 8754 df-n0 8946 df-z 9023 df-dec 9151 df-dvds 11421 |
This theorem is referenced by: (None) |
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