Question

calculati cat mai rapid
$123456^{2}$ -133457 ·123455    
va rog explicati cum ati efectuatttttt !!!

Answer 1

$123456^2-123457\cdot123455=123456^2-(123456+1)(123456-1)=$

$=123456^2-(123456^2-1)=123456^2-123456^2+1=1$