Theorem elabrexg 39206

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 1487	. . . . 5 |- T.
2		csbeq1a 3542	. . . . . . . 8 |- ( x = z -> B = [_ z / x ]_ B )
3	2	equcoms 1947	. . . . . . 7 |- ( z = x -> B = [_ z / x ]_ B )
4		a1tru 1500	. . . . . . 7 |- ( z = x -> T. )
5	3, 4	2thd 255	. . . . . 6 |- ( z = x -> ( B = [_ z / x ]_ B <-> T. ) )
6	5	rspcev 3309	. . . . 5 |- ( ( x e. A /\ T. ) -> E. z e. A B = [_ z / x ]_ B )
7	1, 6	mpan2 707	. . . 4 |- ( x e. A -> E. z e. A B = [_ z / x ]_ B )
8	7	adantr 481	. . 3 |- ( ( x e. A /\ B e. V ) -> E. z e. A B = [_ z / x ]_ B )
9		eqeq1 2626	. . . . . 6 |- ( y = B -> ( y = [_ z / x ]_ B <-> B = [_ z / x ]_ B ) )
10	9	rexbidv 3052	. . . . 5 |- ( y = B -> ( E. z e. A y = [_ z / x ]_ B <-> E. z e. A B = [_ z / x ]_ B ) )
11	10	elabg 3351	. . . 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 482	. . 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 247	. 2 |- ( ( x e. A /\ B e. V ) -> B e. { y | E. z e. A y = [_ z / x ]_ B } )
14		nfv 1843	. . . 4 |- F/ z y = B
15		nfcsb1v 3549	. . . . 5 |- F/_ x [_ z / x ]_ B
16	15	nfeq2 2780	. . . 4 |- F/ x y = [_ z / x ]_ B
17	2	eqeq2d 2632	. . . 4 |- ( x = z -> ( y = B <-> y = [_ z / x ]_ B ) )
18	14, 16, 17	cbvrex 3168	. . 3 |- ( E. x e. A y = B <-> E. z e. A y = [_ z / x ]_ B )
19	18	abbii 2739	. 2 |- { y | E. x e. A y = B } = { y | E. z e. A y = [_ z / x ]_ B }
20	13, 19	syl6eleqr 2712	1 |- ( ( x e. A /\ B e. V ) -> B e. { y | E. x e. A y = B } )

Syntax hints:   -> wi 4   <-> wb 196   /\ wa 384   = wceq 1483   T. wtru 1484   e. wcel 1990   {cab 2608   E.wrex 2913   [_csb 3533

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ral 2917  df-rex 2918  df-v 3202  df-sbc 3436  df-csb 3534

This theorem is referenced by:  upbdrech  39519  ssfiunibd  39523