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Description: Subtract from within a mod calculation. (Contributed by Mario Carneiro, 18-Feb-2014)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | modsubi.1 | |- N e. NN |
|
| modsubi.2 | |- A e. NN |
||
| modsubi.3 | |- B e. NN0 |
||
| modsubi.4 | |- M e. NN0 |
||
| modsubi.6 | |- ( A mod N ) = ( K mod N ) |
||
| modsubi.5 | |- ( M + B ) = K |
||
| Assertion | modsubi | |- ( ( A - B ) mod N ) = ( M mod N ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | modsubi.1 | |- N e. NN |
|
| 2 | modsubi.2 | |- A e. NN |
|
| 3 | modsubi.3 | |- B e. NN0 |
|
| 4 | modsubi.4 | |- M e. NN0 |
|
| 5 | modsubi.6 | |- ( A mod N ) = ( K mod N ) |
|
| 6 | modsubi.5 | |- ( M + B ) = K |
|
| 7 | 2 | nnrei | |- A e. RR |
| 8 | 4 3 | nn0addcli | |- ( M + B ) e. NN0 |
| 9 | 8 | nn0rei | |- ( M + B ) e. RR |
| 10 | 6 9 | eqeltrri | |- K e. RR |
| 11 | 7 10 | pm3.2i | |- ( A e. RR /\ K e. RR ) |
| 12 | 3 | nn0rei | |- B e. RR |
| 13 | 12 | renegcli | |- -u B e. RR |
| 14 | nnrp | |- ( N e. NN -> N e. RR+ ) |
|
| 15 | 1 14 | ax-mp | |- N e. RR+ |
| 16 | 13 15 | pm3.2i | |- ( -u B e. RR /\ N e. RR+ ) |
| 17 | modadd1 | |- ( ( ( A e. RR /\ K e. RR ) /\ ( -u B e. RR /\ N e. RR+ ) /\ ( A mod N ) = ( K mod N ) ) -> ( ( A + -u B ) mod N ) = ( ( K + -u B ) mod N ) ) |
|
| 18 | 11 16 5 17 | mp3an | |- ( ( A + -u B ) mod N ) = ( ( K + -u B ) mod N ) |
| 19 | 2 | nncni | |- A e. CC |
| 20 | 3 | nn0cni | |- B e. CC |
| 21 | 19 20 | negsubi | |- ( A + -u B ) = ( A - B ) |
| 22 | 21 | oveq1i | |- ( ( A + -u B ) mod N ) = ( ( A - B ) mod N ) |
| 23 | 10 | recni | |- K e. CC |
| 24 | 23 20 | negsubi | |- ( K + -u B ) = ( K - B ) |
| 25 | 4 | nn0cni | |- M e. CC |
| 26 | 23 20 25 | subadd2i | |- ( ( K - B ) = M <-> ( M + B ) = K ) |
| 27 | 6 26 | mpbir | |- ( K - B ) = M |
| 28 | 24 27 | eqtri | |- ( K + -u B ) = M |
| 29 | 28 | oveq1i | |- ( ( K + -u B ) mod N ) = ( M mod N ) |
| 30 | 18 22 29 | 3eqtr3i | |- ( ( A - B ) mod N ) = ( M mod N ) |