Description: Swapping order of subtraction doesn't change the absolute value. Example of Apostol p. 363. (Contributed by NM, 1-Oct-1999)
Ref | Expression | ||
---|---|---|---|
Hypotheses | absvalsqi.1 | |
|
abssub.2 | |
||
Assertion | abssubi | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | absvalsqi.1 | |
|
2 | abssub.2 | |
|
3 | abssub | |
|
4 | 1 2 3 | mp2an | |