表示“x与4的差的3倍”的代数式为______； 3120000用科学记数法表示为______．

句型转换。

1. Is this racket yours? (同义句)

    Is this _____ ______?

2. There is one ball under the desk. (对划线部分进行提问) 

    How many _______ ______ there under the desk?

3. Close the window, please. (否定句)

    ______ _______ close the window.

4. My trousers are black and white. (对划线部分进行提问)

    What _______ _______ your trousers?

5. The old man there is a doctor. (对划线部分进行提问)

    ______ ______ the old man there?