Metamath Proof Explorer


Theorem pellfundglb

Description: If a real is larger than the fundamental solution, there is a nontrivial solution less than it. (Contributed by Stefan O'Rear, 18-Sep-2014)

Ref Expression
Assertion pellfundglb ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ∃ 𝑥 ∈ ( Pell1QR ‘ 𝐷 ) ( ( PellFund ‘ 𝐷 ) ≤ 𝑥𝑥 < 𝐴 ) )

Proof

Step Hyp Ref Expression
1 pellfundval ( 𝐷 ∈ ( ℕ ∖ ◻NN ) → ( PellFund ‘ 𝐷 ) = inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) )
2 1 3ad2ant1 ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ( PellFund ‘ 𝐷 ) = inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) )
3 simp3 ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ( PellFund ‘ 𝐷 ) < 𝐴 )
4 2 3 eqbrtrrd ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) < 𝐴 )
5 pellfundre ( 𝐷 ∈ ( ℕ ∖ ◻NN ) → ( PellFund ‘ 𝐷 ) ∈ ℝ )
6 5 3ad2ant1 ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ( PellFund ‘ 𝐷 ) ∈ ℝ )
7 2 6 eqeltrrd ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) ∈ ℝ )
8 simp2 ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → 𝐴 ∈ ℝ )
9 7 8 ltnled ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ( inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) < 𝐴 ↔ ¬ 𝐴 ≤ inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) ) )
10 4 9 mpbid ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ¬ 𝐴 ≤ inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) )
11 ssrab2 { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ⊆ ( Pell14QR ‘ 𝐷 )
12 pell14qrre ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ) → 𝑎 ∈ ℝ )
13 12 ex ( 𝐷 ∈ ( ℕ ∖ ◻NN ) → ( 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) → 𝑎 ∈ ℝ ) )
14 13 ssrdv ( 𝐷 ∈ ( ℕ ∖ ◻NN ) → ( Pell14QR ‘ 𝐷 ) ⊆ ℝ )
15 14 3ad2ant1 ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ( Pell14QR ‘ 𝐷 ) ⊆ ℝ )
16 11 15 sstrid ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ⊆ ℝ )
17 pell1qrss14 ( 𝐷 ∈ ( ℕ ∖ ◻NN ) → ( Pell1QR ‘ 𝐷 ) ⊆ ( Pell14QR ‘ 𝐷 ) )
18 17 3ad2ant1 ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ( Pell1QR ‘ 𝐷 ) ⊆ ( Pell14QR ‘ 𝐷 ) )
19 pellqrex ( 𝐷 ∈ ( ℕ ∖ ◻NN ) → ∃ 𝑎 ∈ ( Pell1QR ‘ 𝐷 ) 1 < 𝑎 )
20 19 3ad2ant1 ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ∃ 𝑎 ∈ ( Pell1QR ‘ 𝐷 ) 1 < 𝑎 )
21 ssrexv ( ( Pell1QR ‘ 𝐷 ) ⊆ ( Pell14QR ‘ 𝐷 ) → ( ∃ 𝑎 ∈ ( Pell1QR ‘ 𝐷 ) 1 < 𝑎 → ∃ 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) 1 < 𝑎 ) )
22 18 20 21 sylc ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ∃ 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) 1 < 𝑎 )
23 rabn0 ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ≠ ∅ ↔ ∃ 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) 1 < 𝑎 )
24 22 23 sylibr ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ≠ ∅ )
25 infmrgelbi ( ( ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ⊆ ℝ ∧ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ≠ ∅ ∧ 𝐴 ∈ ℝ ) ∧ ∀ 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } 𝐴𝑥 ) → 𝐴 ≤ inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) )
26 25 ex ( ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ⊆ ℝ ∧ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ≠ ∅ ∧ 𝐴 ∈ ℝ ) → ( ∀ 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } 𝐴𝑥𝐴 ≤ inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) ) )
27 16 24 8 26 syl3anc ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ( ∀ 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } 𝐴𝑥𝐴 ≤ inf ( { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } , ℝ , < ) ) )
28 10 27 mtod ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ¬ ∀ 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } 𝐴𝑥 )
29 rexnal ( ∃ 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ¬ 𝐴𝑥 ↔ ¬ ∀ 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } 𝐴𝑥 )
30 28 29 sylibr ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ∃ 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ¬ 𝐴𝑥 )
31 breq2 ( 𝑎 = 𝑥 → ( 1 < 𝑎 ↔ 1 < 𝑥 ) )
32 31 elrab ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ↔ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) )
33 simprl ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) ) → 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) )
34 1red ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) ) → 1 ∈ ℝ )
35 simpl1 ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) ) → 𝐷 ∈ ( ℕ ∖ ◻NN ) )
36 pell14qrre ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ) → 𝑥 ∈ ℝ )
37 35 33 36 syl2anc ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) ) → 𝑥 ∈ ℝ )
38 simprr ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) ) → 1 < 𝑥 )
39 34 37 38 ltled ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) ) → 1 ≤ 𝑥 )
40 33 39 jca ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) ) → ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 ≤ 𝑥 ) )
41 elpell1qr2 ( 𝐷 ∈ ( ℕ ∖ ◻NN ) → ( 𝑥 ∈ ( Pell1QR ‘ 𝐷 ) ↔ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 ≤ 𝑥 ) ) )
42 35 41 syl ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) ) → ( 𝑥 ∈ ( Pell1QR ‘ 𝐷 ) ↔ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 ≤ 𝑥 ) ) )
43 40 42 mpbird ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) ) → 𝑥 ∈ ( Pell1QR ‘ 𝐷 ) )
44 32 43 sylan2b ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ) → 𝑥 ∈ ( Pell1QR ‘ 𝐷 ) )
45 44 adantrr ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → 𝑥 ∈ ( Pell1QR ‘ 𝐷 ) )
46 simpl1 ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → 𝐷 ∈ ( ℕ ∖ ◻NN ) )
47 simprl ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } )
48 11 47 sseldi ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) )
49 simpr ( ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) → 1 < 𝑥 )
50 49 a1i ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ( ( 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) → 1 < 𝑥 ) )
51 32 50 syl5bi ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } → 1 < 𝑥 ) )
52 51 imp ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ) → 1 < 𝑥 )
53 52 adantrr ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → 1 < 𝑥 )
54 pellfundlb ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝑥 ∈ ( Pell14QR ‘ 𝐷 ) ∧ 1 < 𝑥 ) → ( PellFund ‘ 𝐷 ) ≤ 𝑥 )
55 46 48 53 54 syl3anc ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → ( PellFund ‘ 𝐷 ) ≤ 𝑥 )
56 simprr ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → ¬ 𝐴𝑥 )
57 15 adantr ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → ( Pell14QR ‘ 𝐷 ) ⊆ ℝ )
58 57 48 sseldd ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → 𝑥 ∈ ℝ )
59 simpl2 ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → 𝐴 ∈ ℝ )
60 58 59 ltnled ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → ( 𝑥 < 𝐴 ↔ ¬ 𝐴𝑥 ) )
61 56 60 mpbird ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → 𝑥 < 𝐴 )
62 55 61 jca ( ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) ∧ ( 𝑥 ∈ { 𝑎 ∈ ( Pell14QR ‘ 𝐷 ) ∣ 1 < 𝑎 } ∧ ¬ 𝐴𝑥 ) ) → ( ( PellFund ‘ 𝐷 ) ≤ 𝑥𝑥 < 𝐴 ) )
63 30 45 62 reximssdv ( ( 𝐷 ∈ ( ℕ ∖ ◻NN ) ∧ 𝐴 ∈ ℝ ∧ ( PellFund ‘ 𝐷 ) < 𝐴 ) → ∃ 𝑥 ∈ ( Pell1QR ‘ 𝐷 ) ( ( PellFund ‘ 𝐷 ) ≤ 𝑥𝑥 < 𝐴 ) )