Question

Fie a,b,c,d ∈ R,astfel incat a+b=20 si c+d=30.Calculati ac+ad+bc+bd.

Answer 1

numai raspunsul direct?

Answer 2

a+b=20
c+d=30
                    ac+ad+bc+bd = a(c+d)+b(c+d)=(c+d)(a+b)=30*20=600 ;