100 de puncte! Rezolvati ce este in imagine urgent!

Explicație:
a) Re=R1+R2+R3= 3+5+7=15 ohm
b) Re=1/(1/R1+1/R2+1/R3)=105/71=1.48 ohm
c) figura de sus: Re=1/(1/R1+1/R2)+R3=15/8+7=8.275 ohm
figura de jos: Re=1/(1/R1+1/R3)+1/R2=1/10+1/5=0.3 ohm