theorem Th3:
for
n,
m,
k being
Nat st
k < m holds
n + k in n + m
scheme
Substitution{
P1[
Nat,
Nat,
natural object ,
Nat,
Nat,
Nat],
F1(
Nat,
Nat,
Nat)
-> natural object } :
for
n being
Nat for
i1,
i2,
i3,
i4,
i5 being
Element of
n holds
{ p where p is b1 -element XFinSequence of NAT : P1[p . i1,p . i2,F1((p . i3),(p . i4),(p . i5)),p . i3,p . i4,p . i5] } is
diophantine Subset of
(n -xtuples_of NAT)
provided
A1:
for
n being
Nat for
i1,
i2,
i3,
i4,
i5,
i6 being
Element of
n holds
{ p where p is b1 -element XFinSequence of NAT : P1[p . i1,p . i2,p . i3,p . i4,p . i5,p . i6] } is
diophantine Subset of
(n -xtuples_of NAT)
and A2:
for
n being
Nat for
i1,
i2,
i3,
i4 being
Element of
n holds
{ p where p is b1 -element XFinSequence of NAT : F1((p . i1),(p . i2),(p . i3)) = p . i4 } is
diophantine Subset of
(n -xtuples_of NAT)
Lm1:
for x, y being Integer
for D being Nat holds
( (x ^2) - (D * (y ^2)) = 1 iff [x,y] is Pell's_solution of D )