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16 sats \ 1 reply \ @Satosora 23 Sep \ parent \ on: (999^2 - 1)/998 charts_and_numbers
doing it on scratch paper helps. I thought it was going to be a lot harder.
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21 sats \ 0 replies \ @south_korea_ln OP 23 Sep
There is a trick.
Hint: remember the formula for (a^2 - b^2)...
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