Step |
Hyp |
Ref |
Expression |
1 |
|
resubval |
|- ( ( A e. RR /\ B e. RR ) -> ( A -R B ) = ( iota_ x e. RR ( B + x ) = A ) ) |
2 |
1
|
eqeq1d |
|- ( ( A e. RR /\ B e. RR ) -> ( ( A -R B ) = C <-> ( iota_ x e. RR ( B + x ) = A ) = C ) ) |
3 |
2
|
3adant3 |
|- ( ( A e. RR /\ B e. RR /\ C e. RR ) -> ( ( A -R B ) = C <-> ( iota_ x e. RR ( B + x ) = A ) = C ) ) |
4 |
|
resubeu |
|- ( ( B e. RR /\ A e. RR ) -> E! x e. RR ( B + x ) = A ) |
5 |
|
oveq2 |
|- ( x = C -> ( B + x ) = ( B + C ) ) |
6 |
5
|
eqeq1d |
|- ( x = C -> ( ( B + x ) = A <-> ( B + C ) = A ) ) |
7 |
6
|
riota2 |
|- ( ( C e. RR /\ E! x e. RR ( B + x ) = A ) -> ( ( B + C ) = A <-> ( iota_ x e. RR ( B + x ) = A ) = C ) ) |
8 |
4 7
|
sylan2 |
|- ( ( C e. RR /\ ( B e. RR /\ A e. RR ) ) -> ( ( B + C ) = A <-> ( iota_ x e. RR ( B + x ) = A ) = C ) ) |
9 |
8
|
3impb |
|- ( ( C e. RR /\ B e. RR /\ A e. RR ) -> ( ( B + C ) = A <-> ( iota_ x e. RR ( B + x ) = A ) = C ) ) |
10 |
9
|
3com13 |
|- ( ( A e. RR /\ B e. RR /\ C e. RR ) -> ( ( B + C ) = A <-> ( iota_ x e. RR ( B + x ) = A ) = C ) ) |
11 |
3 10
|
bitr4d |
|- ( ( A e. RR /\ B e. RR /\ C e. RR ) -> ( ( A -R B ) = C <-> ( B + C ) = A ) ) |