The 91021 Argument Proven

IT'S FINALLY PROVEN a = b = 2 a² = ab a² - b² = ab - b² (a - b)(a + b) = b(a - b) a + b = b (a + b) + 17 = b + 17 21 = 19 9 + 10 = 21 THE END OF THE FAMOUS "91021" ARGUMENT

A blackboard-style mathematical proof appears to show that 9 + 10 equals 21, ending with the claim that the famous “91021” argument is proven. The joke is a deliberately invalid algebraic derivation that divides by zero when cancelling (a − b), parodying confidently presented internet math arguments and the “9+10=21” meme. It is sent as an absurd reaction to fake logic, overconfident proofs, or obviously wrong conclusions.

• @afrosidemoon / 42705 2021-09-12