下列计算正确的是（） A．a3•a2=a6 B．（a2b3）3=a6b C．（_爱下问搜题

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问题选择题

下列计算正确的是（　　）

A．a³•a²=a⁶

B．（a²b³）³=a⁶b

C．（-x）⁵•（-x）³=x⁸

D．（4a）³=12a³

答案

A、应为a³•a²=a³⁺²=a⁵，故本选项错误；

B、应为（a²b³）³=a^2×3b^3×3=a⁶b⁹，故本选项错误；

C、（-x）⁵•（-x）³=（-x）⁸=x⁸，正确；

D、应为（4a）³=4³•a³=64a³，故本选项错误．

故选C．

填空题

选择词组填空。

in common go by deal with in a way share…with as a result as well as
make up with the help of after all watch over win second place
be filled with

1. Will you please ________ my child while I am out?
2. Those two brothers not only look alike, but also they have a lot ________.
3. When I am back to school from sick leave, I will ________ for the missed lessons.
4. ________, he has been very successful.
5. I cannot think of ways to ________ the salesman at the door.
6. I made great progress in English _________ Mr. Lin.
7. Look! Little Tom is in tears. Don't scold him. ________, he is only a boy of six.
8. Three months _______ before I knew about it.
9. Your unbelievable story should be ________ us.
10. When we got the news that we won, the room ________ laughter.

填空题

道岔心轨和护轨工作边距，600mm轨距为（）mm，其偏差为（）。