(1+1/2+1/3+1/6)²-(1+1/2+1/3+1/6)=
facem calculul in paranteza, adica aducem la acelasi numitor 6
(1 + 1/2 + 1/3 + 1/6) = (6 + 3 + 2 + 1)/6 = 2 (calculul unei paranteze)
2² - 2 =
4 - 2 = 2 (adevarat)
(1 + 1/2 + 1/3 + 1/6)² - (1 + 1/2 + 1/3 + 1/6) = 2 (adevarat)
