—_____ I like it a lot.
A:I'm afraid not.
B:Lucky you.
C:What a pain!
D:What a great idea!
巳知二次函数y=a(x2﹣6x+8)(a>0)的图象与x轴分别交于点A、B,与y轴交于点C.点D是抛物线的顶点.
如图,在△ABC中,∠C=90°,AC=2,点D在BC上,∠ADC=2∠B,AD=5,则BC的长为( )