Theorem pnpcan1 | index | src |

theorem pnpcan1 (a b c: nat): $ a + b - (a + c) = b - c $;
StepHypRefExpression
1 eqtr
a + b - (a + c) = b + a - (c + a) -> b + a - (c + a) = b - c -> a + b - (a + c) = b - c
2 subeq
a + b = b + a -> a + c = c + a -> a + b - (a + c) = b + a - (c + a)
3 addcom
a + b = b + a
4 2, 3 ax_mp
a + c = c + a -> a + b - (a + c) = b + a - (c + a)
5 addcom
a + c = c + a
6 4, 5 ax_mp
a + b - (a + c) = b + a - (c + a)
7 1, 6 ax_mp
b + a - (c + a) = b - c -> a + b - (a + c) = b - c
8 pnpcan2
b + a - (c + a) = b - c
9 7, 8 ax_mp
a + b - (a + c) = b - c

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp, itru), axs_pred_calc (ax_gen, ax_4, ax_5, ax_6, ax_7, ax_10, ax_11, ax_12), axs_set (elab, ax_8), axs_the (theid, the0), axs_peano (peano2, peano5, addeq, add0, addS)