The reason I would not write to my teacher the way I write to my friend is because the way you should be writing to your teacher is with respect and be professional.
When you are writing to a teacher you are required to write professionally, respectfully, and formally because they are your superiors and you should speak to them with respect. When you write to a friend you would typically use slang and informal language use because they are your equals.
You would most likely say something like "Dear, Ms. Thomson, I hope this message finds you well. I have contacted you to inform you of a current problem I stumbled uopn while completing a question to one of your assignments."
If you were speaking to a friend you would probably say something like:
" Yooo whatup? How u been? Can you help me on this problem I have no idea what to some"
