Question

Daca a+b=-45 si c+d=50, calculati ac+bc+ad+bd.

Answer 1

ac+bc+ad+bd=c (a+b)+d (a+b)=(a+b)(c
+d)=-45×50=-2250

Answer 2

(a+b)•(c+d) = (-45)•50
a(c+d)+b(c+d)= 2250 =>ac+ad+bc+bd=2250
=>ac+bc+ad+bd=2250