Conversation
Notices
-
♲ @Vincent Pantal🍩ni (panlepan@twitter.com): (a+b)²=a²+2ab+b²
pbs.twimg.com/media/Db5JE_9WsA…-
@miradlo since that, it equals to a²+b(2a+b) (the core formula for manual sqrt method, if anyone remembers it).
…
Moreover, if the first number can be assigned as 10a, and b=5, we'd got:
(10a+b)² = 100a²+20a•5+25=100a(a+1)+25.
Hence, to square any [two-digit] number ending by 5, you should multiply number of tens with one added with 1, and write 25 after that. So, 75²={7·8=56}= 5625.
…
Enjoy! ????
#mathhack
-
