已知A=2x，B是多项式，在计算B+A时，小马虎同学把B+A看成B÷A，结果得x+$\frac{1}{2}$，则B+A=____

（2015•河池）下列物质属于纯净物的是（   ）

 根据对话内容，用方框中所给单词的适当形式填空，每词限用一次。

water    no    Earth    it    for

Bill: I saw a great programme on TV about space yesterday evening.
Tony: What is ____ about?  
Bill: Scientists have discovered ____ on Mars.
Tony: Really? That's very fantastic. Have they discovered life on Mars?
Bill: Well, they're looking____  life but they haven’t found anything yet.
Tony: I know there's ____ life on the moon.
Bill: Yes, that's right. So far there's only life on ____ .
Tony: Are we alone with so many stars in the universe?
Bill: I am interested in it, so I want to be a scientist when I grow up.
Tony: I wish you will.

Rt△ABC中，斜边BC=2，则AB²+AC²+BC²的值为（　　）

若那么的值为   （   ）