a) (27^2 = (30-3)^2 = 900 - 180 + 9 = 729)
б) (19^2 = (20-1)^2 = 400 - 40 + 1 = 361)
в) (215^2 = (200+15)^2 = 40000 + 220015 + 15^2 = 40000 + 6000 + 225 = 46225)
г) (684^2 = (700-16)^2 = 490000 - 270016 + 16^2 = 490000 - 22400 + 256 = 467856)
a) (27^2 = (30-3)^2 = 900 - 180 + 9 = 729)
б) (19^2 = (20-1)^2 = 400 - 40 + 1 = 361)
в) (215^2 = (200+15)^2 = 40000 + 220015 + 15^2 = 40000 + 6000 + 225 = 46225)
г) (684^2 = (700-16)^2 = 490000 - 270016 + 16^2 = 490000 - 22400 + 256 = 467856)