Step |
Hyp |
Ref |
Expression |
1 |
|
neeq1 |
|- ( y = 1 -> ( y =/= 1 <-> 1 =/= 1 ) ) |
2 |
|
eqeq2 |
|- ( y = 1 -> ( ( x + 1 ) = y <-> ( x + 1 ) = 1 ) ) |
3 |
2
|
rexbidv |
|- ( y = 1 -> ( E. x e. NN ( x + 1 ) = y <-> E. x e. NN ( x + 1 ) = 1 ) ) |
4 |
1 3
|
imbi12d |
|- ( y = 1 -> ( ( y =/= 1 -> E. x e. NN ( x + 1 ) = y ) <-> ( 1 =/= 1 -> E. x e. NN ( x + 1 ) = 1 ) ) ) |
5 |
|
neeq1 |
|- ( y = z -> ( y =/= 1 <-> z =/= 1 ) ) |
6 |
|
eqeq2 |
|- ( y = z -> ( ( x + 1 ) = y <-> ( x + 1 ) = z ) ) |
7 |
6
|
rexbidv |
|- ( y = z -> ( E. x e. NN ( x + 1 ) = y <-> E. x e. NN ( x + 1 ) = z ) ) |
8 |
5 7
|
imbi12d |
|- ( y = z -> ( ( y =/= 1 -> E. x e. NN ( x + 1 ) = y ) <-> ( z =/= 1 -> E. x e. NN ( x + 1 ) = z ) ) ) |
9 |
|
neeq1 |
|- ( y = ( z + 1 ) -> ( y =/= 1 <-> ( z + 1 ) =/= 1 ) ) |
10 |
|
eqeq2 |
|- ( y = ( z + 1 ) -> ( ( x + 1 ) = y <-> ( x + 1 ) = ( z + 1 ) ) ) |
11 |
10
|
rexbidv |
|- ( y = ( z + 1 ) -> ( E. x e. NN ( x + 1 ) = y <-> E. x e. NN ( x + 1 ) = ( z + 1 ) ) ) |
12 |
9 11
|
imbi12d |
|- ( y = ( z + 1 ) -> ( ( y =/= 1 -> E. x e. NN ( x + 1 ) = y ) <-> ( ( z + 1 ) =/= 1 -> E. x e. NN ( x + 1 ) = ( z + 1 ) ) ) ) |
13 |
|
neeq1 |
|- ( y = A -> ( y =/= 1 <-> A =/= 1 ) ) |
14 |
|
eqeq2 |
|- ( y = A -> ( ( x + 1 ) = y <-> ( x + 1 ) = A ) ) |
15 |
14
|
rexbidv |
|- ( y = A -> ( E. x e. NN ( x + 1 ) = y <-> E. x e. NN ( x + 1 ) = A ) ) |
16 |
13 15
|
imbi12d |
|- ( y = A -> ( ( y =/= 1 -> E. x e. NN ( x + 1 ) = y ) <-> ( A =/= 1 -> E. x e. NN ( x + 1 ) = A ) ) ) |
17 |
|
df-ne |
|- ( 1 =/= 1 <-> -. 1 = 1 ) |
18 |
|
eqid |
|- 1 = 1 |
19 |
18
|
pm2.24i |
|- ( -. 1 = 1 -> E. x e. NN ( x + 1 ) = 1 ) |
20 |
17 19
|
sylbi |
|- ( 1 =/= 1 -> E. x e. NN ( x + 1 ) = 1 ) |
21 |
|
id |
|- ( z e. NN -> z e. NN ) |
22 |
|
oveq1 |
|- ( x = z -> ( x + 1 ) = ( z + 1 ) ) |
23 |
22
|
eqeq1d |
|- ( x = z -> ( ( x + 1 ) = ( z + 1 ) <-> ( z + 1 ) = ( z + 1 ) ) ) |
24 |
23
|
adantl |
|- ( ( z e. NN /\ x = z ) -> ( ( x + 1 ) = ( z + 1 ) <-> ( z + 1 ) = ( z + 1 ) ) ) |
25 |
|
eqidd |
|- ( z e. NN -> ( z + 1 ) = ( z + 1 ) ) |
26 |
21 24 25
|
rspcedvd |
|- ( z e. NN -> E. x e. NN ( x + 1 ) = ( z + 1 ) ) |
27 |
26
|
2a1d |
|- ( z e. NN -> ( ( z =/= 1 -> E. x e. NN ( x + 1 ) = z ) -> ( ( z + 1 ) =/= 1 -> E. x e. NN ( x + 1 ) = ( z + 1 ) ) ) ) |
28 |
4 8 12 16 20 27
|
nnind |
|- ( A e. NN -> ( A =/= 1 -> E. x e. NN ( x + 1 ) = A ) ) |
29 |
28
|
imp |
|- ( ( A e. NN /\ A =/= 1 ) -> E. x e. NN ( x + 1 ) = A ) |