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In the video, Prof. Loh wrote "Simon's favorite factoring trick". Wonder why it became "someone's".
Since 2021=2025-4=45^2-2^2, which means that 2021 can be written as (45+2)(45-2)=43*47. It's more faster than guessing the numbers and it's more easy to memorize. Although not all numbers can be solved that way
