Description: Reverse the order of subtraction in an equality. (Contributed by Scott Fenton, 8-Jul-2013)
Ref | Expression | ||
---|---|---|---|
Assertion | subeqrev | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | subcl | |
|
2 | subcl | |
|
3 | neg11 | |
|
4 | 1 2 3 | syl2an | |
5 | negsubdi2 | |
|
6 | negsubdi2 | |
|
7 | 5 6 | eqeqan12d | |
8 | 4 7 | bitr3d | |