3 ms·
edit '+ 2 .' should be '+ 25.' so: (x * 10 + 5)^2 = x * x * 10 * 10 + 2 * x * 50 + 25 = x * (x + 1) * 100 + 25.
by onemoreact 15y ago
edit '+ 2 .' should be '+ 25.'
so: (x * 10 + 5)^2 = x * x * 10 * 10 + 2 * x * 50 + 25 = x * (x + 1) * 100 + 25.