Question

Nu am nici cea mai mica idee cum se rezolva...

Answer 1

η₁=R/(R+r₁)<=>η₁R+η₁r₁=R=>η₁r₁=R-η₁R=>r₁=R(1-η₁)/η₁=R(1-0,9)/0,9=0,1R/0,9=0,11R

η₂=R/(R+r₂)<=>η₂R+η₂r₂=R=>η₂r₂=R-η₂R=>r₂=R(1-η₂)/η₂=R(1-0,8)/0,8=0,2R/0,8=0,25R

rs=r₁+r₂=0,11R+0,25R=0,36R

ηs=R/(R+rs)=R/(R+0,36R)=R/1,36R=0,73=73% ->b)