1) 32² = (30+2)² =30² + 2•30•2 + 2² = 900 + 120 + 4 = 1024.
2) 81•79 = (80+1)(80-1) = 80² - 1² = 6400 - 1 = 6399.
1) 32² = (30+2)² =30² + 2•30•2 + 2² = 900 + 120 + 4 = 1024.
2) 81•79 = (80+1)(80-1) = 80² - 1² = 6400 - 1 = 6399.