Hej!
a)
34² = (30 + 4)² = 30² + 2 • 30 • 4 + 4² =
= 900 + 240 + 16 = 1156
b)
89² = (90 - 1)² = 90² - 2 • 90 • 1 + 1² =
= 8100 - 180 + 1 = 7921
c)
73 • 67 = (70 + 3)(70 - 3) =
= 70² - 3² = 4900 - 9 = 4891
Pozdrawiam! - Julka
