Diff. eq. solve linear equation

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The discussion focuses on solving the differential equation 3xy' + y = 12, identified as a linear equation. A participant expresses uncertainty about their solution, particularly regarding the integrating factor. The correct approach involves adjusting the integrating factor calculation by moving the 1/3 into the exponent of ln(x) before simplifying. This results in the integrating factor being x^(1/3), which is confirmed as correct. The conversation emphasizes the importance of proper manipulation of exponential and logarithmic functions in solving differential equations.
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Homework Statement



Solve the following differential equations.

3xy'+y=12

Homework Equations



I believe this is a linear equation problem. So I believed to have solved it, however I am not sure if I have done so correctly.

The Attempt at a Solution


20140301_115639_zps4db21c0a.jpg
 
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If you're not sure, take the derivative and you can verify it from the equation given. The only mistake I see is in calculating your integrating factor:

When you have e^{\frac{1}{3}lnx}, you have to move the 1/3 into the exponent on the lnx before you cancel the e and the ln.
 
jackarms said:
If you're not sure, take the derivative and you can verify it from the equation given. The only mistake I see is in calculating your integrating factor:

When you have e^{\frac{1}{3}lnx}, you have to move the 1/3 into the exponent on the lnx before you cancel the e and the ln.

thank you for the advice.
I see what you mean. so when the e and the ln cancel out, i should be left over with x^(1/3) as my integrating factor correct?
 
Yes, that looks right. That should give you the right answer.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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