R2与R3并联,两电阻两端的电压相等;其电流之和等于流过R1的电流;电流之比等于电阻的反比;故I2:I3=3;2;而I2+I3=I1;故I1:I2:I3=5:3:2;设I1=5I,则I2=3I;I3=2I;由欧姆定律可知:U1=5I;U2=3I×2=6I;U3=2I×3=6I;故电压之比:U1:U2:U3=5;6:6;故答案为:5:3:2,5:6:6.