Description: 2 does not divide -1. That means -1 is odd. (Contributed by AV, 15-Aug-2021)
Ref | Expression | ||
---|---|---|---|
Assertion | n2dvdsm1 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | z0even | |
|
2 | ax-1cn | |
|
3 | neg1cn | |
|
4 | 1pneg1e0 | |
|
5 | 2 3 4 | addcomli | |
6 | 1 5 | breqtrri | |
7 | neg1z | |
|
8 | oddp1even | |
|
9 | 7 8 | ax-mp | |
10 | 6 9 | mpbir | |