Description: Relationship between subtraction and negative. Theorem I.3 of Apostol p. 18. (Contributed by NM, 26-Nov-1994) (Proof shortened by Andrew Salmon, 22-Oct-2011)
Ref | Expression | ||
---|---|---|---|
Hypotheses | negidi.1 | |
|
pncan3i.2 | |
||
Assertion | negsubi | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | negidi.1 | |
|
2 | pncan3i.2 | |
|
3 | negsub | |
|
4 | 1 2 3 | mp2an | |