Original

help me about grammar

What is different between "have somebody to do smt" and "ask someone to do smt"? How to use ? And what is more polite than of them?
Tks !

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First, the correction.

Help me about with grammar

What is different the difference between "have somebody to do smt" and "ask someone to do smt"? How to use do you use them? And what whichis more polite than of them?
Tks !

Now the answer.

It's always more polite to ask.  If you ask someone to do something, you are making a request that they can accept or refuse.  I can ask a friend to help me carry something, or you can ask someone here to help you with grammar.

If you have someone do something, it's an order or a demand. You're saying to him "Do this."  A teacher can have a student write a paper by tomorrow.  A police officer can have someone's house searched.  There's no real choice involved.

Hope it helps!