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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 9418 | . . . 4 ⊢ ;𝐴𝐵 = ((;10 · 𝐴) + 𝐵) | |
2 | 9p1e10 9417 | . . . . . . . 8 ⊢ (9 + 1) = ;10 | |
3 | 2 | eqcomi 2193 | . . . . . . 7 ⊢ ;10 = (9 + 1) |
4 | 3 | oveq1i 5907 | . . . . . 6 ⊢ (;10 · 𝐴) = ((9 + 1) · 𝐴) |
5 | 9cn 9038 | . . . . . . 7 ⊢ 9 ∈ ℂ | |
6 | ax-1cn 7935 | . . . . . . 7 ⊢ 1 ∈ ℂ | |
7 | 3dvdsdec.a | . . . . . . . 8 ⊢ 𝐴 ∈ ℕ0 | |
8 | 7 | nn0cni 9219 | . . . . . . 7 ⊢ 𝐴 ∈ ℂ |
9 | 5, 6, 8 | adddiri 7999 | . . . . . 6 ⊢ ((9 + 1) · 𝐴) = ((9 · 𝐴) + (1 · 𝐴)) |
10 | 8 | mullidi 7991 | . . . . . . 7 ⊢ (1 · 𝐴) = 𝐴 |
11 | 10 | oveq2i 5908 | . . . . . 6 ⊢ ((9 · 𝐴) + (1 · 𝐴)) = ((9 · 𝐴) + 𝐴) |
12 | 4, 9, 11 | 3eqtri 2214 | . . . . 5 ⊢ (;10 · 𝐴) = ((9 · 𝐴) + 𝐴) |
13 | 12 | oveq1i 5907 | . . . 4 ⊢ ((;10 · 𝐴) + 𝐵) = (((9 · 𝐴) + 𝐴) + 𝐵) |
14 | 5, 8 | mulcli 7993 | . . . . 5 ⊢ (9 · 𝐴) ∈ ℂ |
15 | 3dvdsdec.b | . . . . . 6 ⊢ 𝐵 ∈ ℕ0 | |
16 | 15 | nn0cni 9219 | . . . . 5 ⊢ 𝐵 ∈ ℂ |
17 | 14, 8, 16 | addassi 7996 | . . . 4 ⊢ (((9 · 𝐴) + 𝐴) + 𝐵) = ((9 · 𝐴) + (𝐴 + 𝐵)) |
18 | 1, 13, 17 | 3eqtri 2214 | . . 3 ⊢ ;𝐴𝐵 = ((9 · 𝐴) + (𝐴 + 𝐵)) |
19 | 18 | breq2i 4026 | . 2 ⊢ (3 ∥ ;𝐴𝐵 ↔ 3 ∥ ((9 · 𝐴) + (𝐴 + 𝐵))) |
20 | 3z 9313 | . . 3 ⊢ 3 ∈ ℤ | |
21 | 7 | nn0zi 9306 | . . . 4 ⊢ 𝐴 ∈ ℤ |
22 | 15 | nn0zi 9306 | . . . 4 ⊢ 𝐵 ∈ ℤ |
23 | zaddcl 9324 | . . . 4 ⊢ ((𝐴 ∈ ℤ ∧ 𝐵 ∈ ℤ) → (𝐴 + 𝐵) ∈ ℤ) | |
24 | 21, 22, 23 | mp2an 426 | . . 3 ⊢ (𝐴 + 𝐵) ∈ ℤ |
25 | 9nn 9118 | . . . . . 6 ⊢ 9 ∈ ℕ | |
26 | 25 | nnzi 9305 | . . . . 5 ⊢ 9 ∈ ℤ |
27 | zmulcl 9337 | . . . . 5 ⊢ ((9 ∈ ℤ ∧ 𝐴 ∈ ℤ) → (9 · 𝐴) ∈ ℤ) | |
28 | 26, 21, 27 | mp2an 426 | . . . 4 ⊢ (9 · 𝐴) ∈ ℤ |
29 | zmulcl 9337 | . . . . . . 7 ⊢ ((3 ∈ ℤ ∧ 𝐴 ∈ ℤ) → (3 · 𝐴) ∈ ℤ) | |
30 | 20, 21, 29 | mp2an 426 | . . . . . 6 ⊢ (3 · 𝐴) ∈ ℤ |
31 | dvdsmul1 11855 | . . . . . 6 ⊢ ((3 ∈ ℤ ∧ (3 · 𝐴) ∈ ℤ) → 3 ∥ (3 · (3 · 𝐴))) | |
32 | 20, 30, 31 | mp2an 426 | . . . . 5 ⊢ 3 ∥ (3 · (3 · 𝐴)) |
33 | 3t3e9 9107 | . . . . . . . 8 ⊢ (3 · 3) = 9 | |
34 | 33 | eqcomi 2193 | . . . . . . 7 ⊢ 9 = (3 · 3) |
35 | 34 | oveq1i 5907 | . . . . . 6 ⊢ (9 · 𝐴) = ((3 · 3) · 𝐴) |
36 | 3cn 9025 | . . . . . . 7 ⊢ 3 ∈ ℂ | |
37 | 36, 36, 8 | mulassi 7997 | . . . . . 6 ⊢ ((3 · 3) · 𝐴) = (3 · (3 · 𝐴)) |
38 | 35, 37 | eqtri 2210 | . . . . 5 ⊢ (9 · 𝐴) = (3 · (3 · 𝐴)) |
39 | 32, 38 | breqtrri 4045 | . . . 4 ⊢ 3 ∥ (9 · 𝐴) |
40 | 28, 39 | pm3.2i 272 | . . 3 ⊢ ((9 · 𝐴) ∈ ℤ ∧ 3 ∥ (9 · 𝐴)) |
41 | dvdsadd2b 11882 | . . 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 1348 | . 2 ⊢ (3 ∥ (𝐴 + 𝐵) ↔ 3 ∥ ((9 · 𝐴) + (𝐴 + 𝐵))) |
43 | 19, 42 | bitr4i 187 | 1 ⊢ (3 ∥ ;𝐴𝐵 ↔ 3 ∥ (𝐴 + 𝐵)) |
Colors of variables: wff set class |
Syntax hints: ∧ wa 104 ↔ wb 105 ∈ wcel 2160 class class class wbr 4018 (class class class)co 5897 0cc0 7842 1c1 7843 + caddc 7845 · cmul 7847 3c3 9002 9c9 9008 ℕ0cn0 9207 ℤcz 9284 ;cdc 9415 ∥ cdvds 11829 |
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-in1 615 ax-in2 616 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 4192 ax-pr 4227 ax-un 4451 ax-setind 4554 ax-cnex 7933 ax-resscn 7934 ax-1cn 7935 ax-1re 7936 ax-icn 7937 ax-addcl 7938 ax-addrcl 7939 ax-mulcl 7940 ax-mulrcl 7941 ax-addcom 7942 ax-mulcom 7943 ax-addass 7944 ax-mulass 7945 ax-distr 7946 ax-i2m1 7947 ax-0lt1 7948 ax-1rid 7949 ax-0id 7950 ax-rnegex 7951 ax-cnre 7953 ax-pre-ltirr 7954 ax-pre-ltwlin 7955 ax-pre-lttrn 7956 ax-pre-ltadd 7958 |
This theorem depends on definitions: df-bi 117 df-3or 981 df-3an 982 df-tru 1367 df-fal 1370 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-ne 2361 df-nel 2456 df-ral 2473 df-rex 2474 df-reu 2475 df-rab 2477 df-v 2754 df-sbc 2978 df-dif 3146 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-id 4311 df-xp 4650 df-rel 4651 df-cnv 4652 df-co 4653 df-dm 4654 df-iota 5196 df-fun 5237 df-fv 5243 df-riota 5852 df-ov 5900 df-oprab 5901 df-mpo 5902 df-pnf 8025 df-mnf 8026 df-xr 8027 df-ltxr 8028 df-le 8029 df-sub 8161 df-neg 8162 df-inn 8951 df-2 9009 df-3 9010 df-4 9011 df-5 9012 df-6 9013 df-7 9014 df-8 9015 df-9 9016 df-n0 9208 df-z 9285 df-dec 9416 df-dvds 11830 |
This theorem is referenced by: (None) |
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