Theorem elabrexg 5761

Description: Elementhood in an image set. (Contributed by Glauco Siliprandi, 11-Dec-2019.)

Assertion

Ref	Expression
elabrexg	|- ( ( x e. A /\ B e. V ) -> B e. { y | E. x e. A y = B } )

Distinct variable groups:   x, A, y   y, B

Allowed substitution hints:   B( x)   V( x, y)

Proof of Theorem elabrexg

Dummy variable z is distinct from all other variables.

Step	Hyp	Ref	Expression
1		tru 1357	. . . . 5 |- T.
2		csbeq1a 3068	. . . . . . . 8 |- ( x = z -> B = [_ z / x ]_ B )
3	2	equcoms 1708	. . . . . . 7 |- ( z = x -> B = [_ z / x ]_ B )
4		trud 1369	. . . . . . 7 |- ( z = x -> T. )
5	3, 4	2thd 175	. . . . . 6 |- ( z = x -> ( B = [_ z / x ]_ B <-> T. ) )
6	5	rspcev 2843	. . . . 5 |- ( ( x e. A /\ T. ) -> E. z e. A B = [_ z / x ]_ B )
7	1, 6	mpan2 425	. . . 4 |- ( x e. A -> E. z e. A B = [_ z / x ]_ B )
8	7	adantr 276	. . 3 |- ( ( x e. A /\ B e. V ) -> E. z e. A B = [_ z / x ]_ B )
9		eqeq1 2184	. . . . . 6 |- ( y = B -> ( y = [_ z / x ]_ B <-> B = [_ z / x ]_ B ) )
10	9	rexbidv 2478	. . . . 5 |- ( y = B -> ( E. z e. A y = [_ z / x ]_ B <-> E. z e. A B = [_ z / x ]_ B ) )
11	10	elabg 2885	. . . 4 |- ( B e. V -> ( B e. { y | E. z e. A y = [_ z / x ]_ B } <-> E. z e. A B = [_ z / x ]_ B ) )
12	11	adantl 277	. . 3 |- ( ( x e. A /\ B e. V ) -> ( B e. { y | E. z e. A y = [_ z / x ]_ B } <-> E. z e. A B = [_ z / x ]_ B ) )
13	8, 12	mpbird 167	. 2 |- ( ( x e. A /\ B e. V ) -> B e. { y | E. z e. A y = [_ z / x ]_ B } )
14		nfv 1528	. . . 4 |- F/ z y = B
15		nfcsb1v 3092	. . . . 5 |- F/_ x [_ z / x ]_ B
16	15	nfeq2 2331	. . . 4 |- F/ x y = [_ z / x ]_ B
17	2	eqeq2d 2189	. . . 4 |- ( x = z -> ( y = B <-> y = [_ z / x ]_ B ) )
18	14, 16, 17	cbvrexw 2700	. . 3 |- ( E. x e. A y = B <-> E. z e. A y = [_ z / x ]_ B )
19	18	abbii 2293	. 2 |- { y | E. x e. A y = B } = { y | E. z e. A y = [_ z / x ]_ B }
20	13, 19	eleqtrrdi 2271	1 |- ( ( x e. A /\ B e. V ) -> B e. { y | E. x e. A y = B } )

Syntax hints:   -> wi 4   /\ wa 104   <-> wb 105   = wceq 1353   T. wtru 1354   e. wcel 2148   {cab 2163   E.wrex 2456   [_csb 3059

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-io 709  ax-5 1447  ax-7 1448  ax-gen 1449  ax-ie1 1493  ax-ie2 1494  ax-8 1504  ax-10 1505  ax-11 1506  ax-i12 1507  ax-bndl 1509  ax-4 1510  ax-17 1526  ax-i9 1530  ax-ial 1534  ax-i5r 1535  ax-ext 2159

This theorem depends on definitions:  df-bi 117  df-tru 1356  df-nf 1461  df-sb 1763  df-clab 2164  df-cleq 2170  df-clel 2173  df-nfc 2308  df-rex 2461  df-v 2741  df-sbc 2965  df-csb 3060

This theorem is referenced by:  lss1d  13475