3 ms·
That's still a bit slower than it needs to be. The real trick to doing something like is seeing that we have 10(18x16) = 10(17^2 - 1) = 10(289-1) Having the fi
by eachro 11y ago
That's still a bit slower than it needs to be. The real trick to doing something like is seeing that we have 10(18x16) = 10(17^2 - 1) = 10(289-1)
Having the first 30 squares committed to memory has been pretty useful for me.
- bumbledraven 11y agoRight. And just to be explicit, we're using the fact that (x+1)(x-1) = x² -1. So to add in that step, it would be: 18 x 16 = (17+1)(17-1) = 10(17²-1)