P1=U^2/(5+R1)^2 *R1
P1'=U^2/R1
由P1 :P1'=4 :9得:U^2/(5+R1)^2 *R1 / U^2/R1 =4:9 R1=10Ω
I1=U/(5+R1)=U/15
R1R2并联电阻R=R1R2/(R1+R2)=10*8/(10+8)=40/9 Ω
I2=U/R=9U/40
I1:I2=8:27
P1=U^2/(5+R1)^2 *R1
P1'=U^2/R1
由P1 :P1'=4 :9得:U^2/(5+R1)^2 *R1 / U^2/R1 =4:9 R1=10Ω
I1=U/(5+R1)=U/15
R1R2并联电阻R=R1R2/(R1+R2)=10*8/(10+8)=40/9 Ω
I2=U/R=9U/40
I1:I2=8:27