如图，L1∥L2∥L3，B1B2=二分之一B2B3，又A1B1=1，A3B3=3，则A2B2=..... 【主要还是看图

Question

如题所述

Answer 1

PB1:PB3=A1B1:A3B3=1:3
PB1=(1/3)PB3=(1/3)(PB1+B1B2+B2B3)=(1/3)(PB1+B2B3/2+B2B3)=(1/3)[PB1+(3/2)B2B3]
PB1-(1/3)PB1=(1/2)B2B3
PB1=(3/4)B2B3;
PB1:PB2=A1B1:A2B2
(3/4)B2B3:(PB1+B1B2)=1:A2B2
(3/4)B2B3:[(3/4)B2B3+(1/2)B2B3]=1:A2B2
A2B2=(5/4)/(3/4)=5/3;
PA1:A1A2=PB1:B1B2=(3/4)B2B3:(1/2)B2B3=3/2;