Question

1 将线段AB延长至C,使BC=1/3AB（BC=三分之一AB）,延长BC至D,使CD=1/3BC,延长CD至E,是DE

Answer 1

1.设AB长度=a

BC=1/3a

CD=1/3*1/3a

DE=1/3*1/3*1/3a

AE=a+1/3a+1/3*1/3a+1/3*1/3*1/3a=80 =>a=54

2.AB=5,AC=7 =>BC=2

BC=2 BD=4BC =>BD=8

BC-AB=AD =>AD=3

=>CD=10

=>DE(CE)=5

DE-AD=AE =>5-3=2

AE=2,CD=10 =>AE=1/5CD