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Question 4 (a) 

Find the function that satisfies and 
Make sure you understand the problem fully: What is the question asking you to do? Are there specific conditions or constraints that you should take note of? How will you know if your answer is correct from your work only? Can you rephrase the question in your own words in a way that makes sense to you? 
If you are stuck, check the hint below. Consider it for a while. Does it give you a new idea on how to approach the problem? If so, try it! 
Hint 

Try separation of variables method. 
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Solution 

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Please rate my easiness! It's quick and helps everyone guide their studies. We separate the variables (cross multiply to have at one side, at the other side):
Now integrate:
Plugging in and gives: and so . This implies . or ±
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