优质解答
设BC=x
x(50-x)/2=300
50x-x^2=600
x^2-50x+600=0
(x-20)(x-30)=0
x1=20, x2=30(舍去)
BC=20
AB=CD=15
设BC=x
x(50-x)/2=300
50x-x^2=600
x^2-50x+600=0
(x-20)(x-30)=0
x1=20, x2=30(舍去)
BC=20
AB=CD=15