Immortal Truth
In Scripta Mathematica, March 1955, Pedro A. Pisa offers an unkillably valid equation:
123789 + 561945 + 642864 = 242868 + 323787 + 761943
Hack away at its terms, from either end, and it remains true:

Stab it in the heart, removing the two center digits from each term, and it still balances:
1289 + 5645 + 6464 = 2468 + 3287 + 7643
Do this again and it still balances:
19 + 55 + 64 = 28 + 37 + 73
Most amazing: You can square every term above, in every equation, and they’ll all remain true.