只要结果}}}
AD=DE=X
AB=BE=3
EC=5-3=2
AC^2=BC^2-AB^2=16
AC=4
DC^2=EC^2+DE^2
(4-AD)^2=4+AD^2
AD=2.5
BD^2=3^2+2.5^2
=12.75
BD=0.5√51
所以三角形ABD的周长=5.5+0.5√51