Объяснение:
U2=U3=U4=I4*R4=3*8=24 B
r234=R2*R3*R4 / (R2*R3+R3*R4+R2*R4)=4*12*8 * (4*12+12*8+4*8)= 2.18 Ом
I1=U2/r234 = 24/2.18=11.01 A
Uав = I1 * (R1+r234) =11.01*(5+2.18)=79.05 B
P1 = I^2*R1 = 11.01^2 * 5=606.1 Ватт
