(1)2a^2+b^2+c^2-2ab-8a-4c+20=0
(a^2-8a+16)+(a^2-2ab+b^2)+(c^2-4c+4)=0
(a-4)^2+(a-b)^2+(c-2)^2=0
a-4=0, a-b=0, c-2=0
a=b=4, c=2
(2)A(16,0),B(0,4),C(0,2)
AC的解析式是:x/16+y/2=1,y=-1/8x+2
OE垂直AC,所以OE的解析式为:y=8x
AB的解析式为:x/16+y/4=1,y=-1/4x+4
解方程组:y=8x,y=-1/4x+4
x=16/33,y=128/33
D的坐标是(16/33,128/33)