Theorem 4sqexercise1 12594

Description: Exercise which may help in understanding the proof of 4sqlemsdc 12596. (Contributed by Jim Kingdon, 25-May-2025.)

Hypothesis

Ref	Expression
4sqexercise1.s	⊢ 𝑆 = {𝑛 ∣ ∃𝑥 ∈ ℤ 𝑛 = (𝑥↑2)}

Assertion

Ref	Expression
4sqexercise1	⊢ (𝐴 ∈ ℕ0 → DECID 𝐴 ∈ 𝑆)

Distinct variable group:   𝐴,𝑛,𝑥

Allowed substitution hints:   𝑆(𝑥,𝑛)

Proof of Theorem 4sqexercise1

Step	Hyp	Ref	Expression
1		nn0negz 9379	. . . 4 ⊢ (𝐴 ∈ ℕ0 → -𝐴 ∈ ℤ)
2		nn0z 9365	. . . 4 ⊢ (𝐴 ∈ ℕ0 → 𝐴 ∈ ℤ)
3		elfzelz 10119	. . . . . . 7 ⊢ (𝑥 ∈ (-𝐴...𝐴) → 𝑥 ∈ ℤ)
4	3	adantl 277	. . . . . 6 ⊢ ((𝐴 ∈ ℕ0 ∧ 𝑥 ∈ (-𝐴...𝐴)) → 𝑥 ∈ ℤ)
5		zsqcl 10721	. . . . . 6 ⊢ (𝑥 ∈ ℤ → (𝑥↑2) ∈ ℤ)
6	4, 5	syl 14	. . . . 5 ⊢ ((𝐴 ∈ ℕ0 ∧ 𝑥 ∈ (-𝐴...𝐴)) → (𝑥↑2) ∈ ℤ)
7		zdceq 9420	. . . . 5 ⊢ ((𝐴 ∈ ℤ ∧ (𝑥↑2) ∈ ℤ) → DECID 𝐴 = (𝑥↑2))
8	2, 6, 7	syl2an2r 595	. . . 4 ⊢ ((𝐴 ∈ ℕ0 ∧ 𝑥 ∈ (-𝐴...𝐴)) → DECID 𝐴 = (𝑥↑2))
9	1, 2, 8	exfzdc 10335	. . 3 ⊢ (𝐴 ∈ ℕ0 → DECID ∃𝑥 ∈ (-𝐴...𝐴)𝐴 = (𝑥↑2))
10		simpr 110	. . . . . . . . . . 11 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → 𝐴 = (𝑥↑2))
11		zsqcl2 10728	. . . . . . . . . . . 12 ⊢ (𝑥 ∈ ℤ → (𝑥↑2) ∈ ℕ0)
12	11	adantr 276	. . . . . . . . . . 11 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → (𝑥↑2) ∈ ℕ0)
13	10, 12	eqeltrd 2273	. . . . . . . . . 10 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → 𝐴 ∈ ℕ0)
14	13	nn0zd 9465	. . . . . . . . 9 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → 𝐴 ∈ ℤ)
15	14	znegcld 9469	. . . . . . . 8 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → -𝐴 ∈ ℤ)
16		simpl 109	. . . . . . . 8 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → 𝑥 ∈ ℤ)
17		zre 9349	. . . . . . . . . 10 ⊢ (𝑥 ∈ ℤ → 𝑥 ∈ ℝ)
18	17	adantr 276	. . . . . . . . 9 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → 𝑥 ∈ ℝ)
19	13	nn0red 9322	. . . . . . . . 9 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → 𝐴 ∈ ℝ)
20		znegcl 9376	. . . . . . . . . . . . 13 ⊢ (𝑥 ∈ ℤ → -𝑥 ∈ ℤ)
21		zzlesq 10819	. . . . . . . . . . . . 13 ⊢ (-𝑥 ∈ ℤ → -𝑥 ≤ (-𝑥↑2))
22	20, 21	syl 14	. . . . . . . . . . . 12 ⊢ (𝑥 ∈ ℤ → -𝑥 ≤ (-𝑥↑2))
23	22	adantr 276	. . . . . . . . . . 11 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → -𝑥 ≤ (-𝑥↑2))
24		zcn 9350	. . . . . . . . . . . . 13 ⊢ (𝑥 ∈ ℤ → 𝑥 ∈ ℂ)
25		sqneg 10709	. . . . . . . . . . . . 13 ⊢ (𝑥 ∈ ℂ → (-𝑥↑2) = (𝑥↑2))
26	24, 25	syl 14	. . . . . . . . . . . 12 ⊢ (𝑥 ∈ ℤ → (-𝑥↑2) = (𝑥↑2))
27	26	adantr 276	. . . . . . . . . . 11 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → (-𝑥↑2) = (𝑥↑2))
28	23, 27	breqtrd 4060	. . . . . . . . . 10 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → -𝑥 ≤ (𝑥↑2))
29	28, 10	breqtrrd 4062	. . . . . . . . 9 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → -𝑥 ≤ 𝐴)
30	18, 19, 29	lenegcon1d 8573	. . . . . . . 8 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → -𝐴 ≤ 𝑥)
31		zzlesq 10819	. . . . . . . . . 10 ⊢ (𝑥 ∈ ℤ → 𝑥 ≤ (𝑥↑2))
32	31	adantr 276	. . . . . . . . 9 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → 𝑥 ≤ (𝑥↑2))
33	32, 10	breqtrrd 4062	. . . . . . . 8 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → 𝑥 ≤ 𝐴)
34	15, 14, 16, 30, 33	elfzd 10110	. . . . . . 7 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → 𝑥 ∈ (-𝐴...𝐴))
35	34, 10	jca 306	. . . . . 6 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) → (𝑥 ∈ (-𝐴...𝐴) ∧ 𝐴 = (𝑥↑2)))
36	3	anim1i 340	. . . . . 6 ⊢ ((𝑥 ∈ (-𝐴...𝐴) ∧ 𝐴 = (𝑥↑2)) → (𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)))
37	35, 36	impbii 126	. . . . 5 ⊢ ((𝑥 ∈ ℤ ∧ 𝐴 = (𝑥↑2)) ↔ (𝑥 ∈ (-𝐴...𝐴) ∧ 𝐴 = (𝑥↑2)))
38	37	rexbii2 2508	. . . 4 ⊢ (∃𝑥 ∈ ℤ 𝐴 = (𝑥↑2) ↔ ∃𝑥 ∈ (-𝐴...𝐴)𝐴 = (𝑥↑2))
39	38	dcbii 841	. . 3 ⊢ (DECID ∃𝑥 ∈ ℤ 𝐴 = (𝑥↑2) ↔ DECID ∃𝑥 ∈ (-𝐴...𝐴)𝐴 = (𝑥↑2))
40	9, 39	sylibr 134	. 2 ⊢ (𝐴 ∈ ℕ0 → DECID ∃𝑥 ∈ ℤ 𝐴 = (𝑥↑2))
41		eqeq1 2203	. . . . 5 ⊢ (𝑛 = 𝐴 → (𝑛 = (𝑥↑2) ↔ 𝐴 = (𝑥↑2)))
42	41	rexbidv 2498	. . . 4 ⊢ (𝑛 = 𝐴 → (∃𝑥 ∈ ℤ 𝑛 = (𝑥↑2) ↔ ∃𝑥 ∈ ℤ 𝐴 = (𝑥↑2)))
43		4sqexercise1.s	. . . 4 ⊢ 𝑆 = {𝑛 ∣ ∃𝑥 ∈ ℤ 𝑛 = (𝑥↑2)}
44	42, 43	elab2g 2911	. . 3 ⊢ (𝐴 ∈ ℕ0 → (𝐴 ∈ 𝑆 ↔ ∃𝑥 ∈ ℤ 𝐴 = (𝑥↑2)))
45	44	dcbid 839	. 2 ⊢ (𝐴 ∈ ℕ0 → (DECID 𝐴 ∈ 𝑆 ↔ DECID ∃𝑥 ∈ ℤ 𝐴 = (𝑥↑2)))
46	40, 45	mpbird 167	1 ⊢ (𝐴 ∈ ℕ0 → DECID 𝐴 ∈ 𝑆)

Syntax hints:   → wi 4   ∧ wa 104  DECID wdc 835   = wceq 1364   ∈ wcel 2167  {cab 2182  ∃wrex 2476   class class class wbr 4034  (class class class)co 5925  ℂcc 7896  ℝcr 7897   ≤ cle 8081  -cneg 8217  2c2 9060  ℕ₀cn0 9268  ℤcz 9345  ...cfz 10102  ↑cexp 10649

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 1461  ax-7 1462  ax-gen 1463  ax-ie1 1507  ax-ie2 1508  ax-8 1518  ax-10 1519  ax-11 1520  ax-i12 1521  ax-bndl 1523  ax-4 1524  ax-17 1540  ax-i9 1544  ax-ial 1548  ax-i5r 1549  ax-13 2169  ax-14 2170  ax-ext 2178  ax-coll 4149  ax-sep 4152  ax-nul 4160  ax-pow 4208  ax-pr 4243  ax-un 4469  ax-setind 4574  ax-iinf 4625  ax-cnex 7989  ax-resscn 7990  ax-1cn 7991  ax-1re 7992  ax-icn 7993  ax-addcl 7994  ax-addrcl 7995  ax-mulcl 7996  ax-mulrcl 7997  ax-addcom 7998  ax-mulcom 7999  ax-addass 8000  ax-mulass 8001  ax-distr 8002  ax-i2m1 8003  ax-0lt1 8004  ax-1rid 8005  ax-0id 8006  ax-rnegex 8007  ax-precex 8008  ax-cnre 8009  ax-pre-ltirr 8010  ax-pre-ltwlin 8011  ax-pre-lttrn 8012  ax-pre-apti 8013  ax-pre-ltadd 8014  ax-pre-mulgt0 8015  ax-pre-mulext 8016

This theorem depends on definitions:  df-bi 117  df-dc 836  df-3or 981  df-3an 982  df-tru 1367  df-fal 1370  df-nf 1475  df-sb 1777  df-eu 2048  df-mo 2049  df-clab 2183  df-cleq 2189  df-clel 2192  df-nfc 2328  df-ne 2368  df-nel 2463  df-ral 2480  df-rex 2481  df-reu 2482  df-rmo 2483  df-rab 2484  df-v 2765  df-sbc 2990  df-csb 3085  df-dif 3159  df-un 3161  df-in 3163  df-ss 3170  df-nul 3452  df-if 3563  df-pw 3608  df-sn 3629  df-pr 3630  df-op 3632  df-uni 3841  df-int 3876  df-iun 3919  df-br 4035  df-opab 4096  df-mpt 4097  df-tr 4133  df-id 4329  df-po 4332  df-iso 4333  df-iord 4402  df-on 4404  df-ilim 4405  df-suc 4407  df-iom 4628  df-xp 4670  df-rel 4671  df-cnv 4672  df-co 4673  df-dm 4674  df-rn 4675  df-res 4676  df-ima 4677  df-iota 5220  df-fun 5261  df-fn 5262  df-f 5263  df-f1 5264  df-fo 5265  df-f1o 5266  df-fv 5267  df-riota 5880  df-ov 5928  df-oprab 5929  df-mpo 5930  df-1st 6207  df-2nd 6208  df-recs 6372  df-frec 6458  df-pnf 8082  df-mnf 8083  df-xr 8084  df-ltxr 8085  df-le 8086  df-sub 8218  df-neg 8219  df-reap 8621  df-ap 8628  df-div 8719  df-inn 9010  df-2 9068  df-n0 9269  df-z 9346  df-uz 9621  df-fz 10103  df-fzo 10237  df-seqfrec 10559  df-exp 10650

This theorem is referenced by: (None)