Science:Math Exam Resources/Courses/MATH101/April 2010/Question 09
Check out our new website www.mathexamresources.com. 
Question 09 

For any real number , define . Find the minimum value of . 
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 

We can consider as a constant inside the integral 
Checking a solution serves two purposes: helping you if, after having used the hint, you still are stuck on the problem; or if you have solved the problem and would like to check your work.

Solution 

Found a typo? Is this solution unclear? Let us know here.
Please rate my easiness! It's quick and helps everyone guide their studies. First we solve the integral considering as a constant:
The first integral in the sum is
Now we solve by parts letting and so that and . Hence
The last integral in the sum is:
So
The derivative is directly computed to be:
Which is zero at . To make sure it is a minimum we use the second derivative test. The second derivative is:
Which is always positive (Remember that ). This means is the minimum for . Plugging in this value gives

Please rate how easy you found this problem:
Current user rating: 42/100 (5 votes)
Hard Easy 
Click here for similar questions
MER QGH flag, MER QGQ flag, MER QGS flag, MER RT flag, MER Tag Integration by parts, MER Tag Optimization 