Question

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

Answer 1

ac+ad+bc+bd=a(c+d)+b(c+d)=(c+d)(a+d)
Cred ca a doua egalitate este: c+d=30
In acest caz avem in continuare:
(c+d)(a+b)=30·20=600
Spor la lucru!