Exercitiul este gresit copiat.
Corect el trebuie sa arate asa(cred):\(a+c)(b+c)(b^2+c^2-bc)=(b^2+c^2)(ab minus c^2)
Rezolvare:intro progresie geometrica a=a;b=aq;c=aq^2
(a+c)(b^3-c^3)=(b^2+c^2)(ab+c^2)
(a+aq^2)(a^3q^3-a^3q^6)=(a^2q^2+a^2q^4)(a^2q-a^2q^4)
a^4q^3(1+q^2)(1-q^3)=a^4q^3(1+q^2)(1-q^3) ok
