高岭土的组成可表示为Al₂Si₂O_x（OH）_y，其中x、y的数值分别为（　　）

①小肠长约5～6米②小肠内表面有许多环形皱襞③皱襞表面有许多小肠绒毛④小肠壁内有许多肠腺

    Do you w____your own blog(博客)？Do you often r____others' blogs on the Internet?

All ____ the world, not only famous people but also many students use b____ to share their e____ and ask for advice or help. "It's a good way to ____ my life to the world, "a student says. She has had her blog f____ eight months. Students like ____(write) blogs. O____you start to write your blog, you will find that you o____up a new world. But what you write down may trouble you sometimes. So, use the blog carefully so that you can keep yourself away from some trouble. The blog makes everybody's life colorful.

如图，在平行四边形ABCD中，点E是BC的中点，∠BOE=30°，OD=2，cos∠ADB=$\frac{\sqrt{3}}{2}$．则CD=____ 

设x₁、x₂是一元二次方程x²+x﹣3=0的两根，则x₁³﹣4x₂²+15等于（　　）