Description: Law for double subtraction. (Contributed by NM, 19-Aug-2005) (Revised by Mario Carneiro, 27-May-2016)
Ref | Expression | ||
---|---|---|---|
Assertion | subsub4 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nppcan2 | |
|
2 | simp1 | |
|
3 | simp2 | |
|
4 | subcl | |
|
5 | 2 3 4 | syl2anc | |
6 | simp3 | |
|
7 | 3 6 | addcld | |
8 | subcl | |
|
9 | 2 7 8 | syl2anc | |
10 | subadd2 | |
|
11 | 5 6 9 10 | syl3anc | |
12 | 1 11 | mpbird | |