Question

Aratati ca pentru orice numerele a,b,c are loc identitatea:

(a+b+c)²=a²+b²+c²+2ab+2ac+2bc

dau coroana si 17 puncte

Answer 1

[tex](a+b+c)^2=(a+b+c)(a+b+c)=\\ a^2+ab+ac+ab+b^2+bc+ca+cb+c^2=a^2+b^2+c^2+\\ +2ab+2ac+2bc[/tex]