# Thread: I have a problem in finding the long run cost curve from an short-run cost equation

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## I have a problem in finding the long run cost curve from an short-run cost equation

Hi, I have a problem in finding the long run cost curve from a short-run cost equation. I do not know whether this is the right forum for me to ask this question. But the question is as follows:

Suppose a firm's short-run cost curve for any given level of capital K is "C (K, Q) = bK^2(1 + (Q/K)^4)". Find the equation of the long run cost curve.

Can someone show me in detail how to obtain the long run cost curve? and can someone suggest me a forum which I can ask and discuss Economics questions?

Thank you very much XD

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never ceases to make me chuckle...

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This is the wrong forum.

Can someone show me in detail how to obtain the long run cost curve?
Long run - Wikipedia, the free encyclopedia

and can someone suggest me a forum which I can ask and discuss Economics questions?

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When in doubt, just set MR=MC.

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Why is everybody being so mean to this guy? Why not just answer his/her question and let him be on his way? I kind of like helping solve the occasional problem. To solve, all you have to do is minimize the cost function wrt K (set the derivate wrt to K equal to zero, then solve for K), then substitute in the value of K* (the optimal K) back into the original cost function. This will be the long run cost curve as a function of Q. Check out the "envelope theorem" for more help with this type of problem.

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I agree with kevin--we should be more tolerant of the occasional homework question. Although, I think its time for somebody to set up a forum reserved strictly for economics homework questions. They have one for physics (Homework & Coursework Questions Forum

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Yahoo answers is actually a good place to ask these kinds of questions. I post answers to questions like this fairly often over there, but I won't do it here.

People are being mean about it because this is one of very few places on the internet where upper-division economics students can get together and discuss graduate school options and strategies, but there are already other places where one can ask homework questions (both free and paid). If principles students find out that it's also a homework forum, we'll pretty much lose the actual purpose of the forum. The recent question on quintile regression methods was annoying enough, but we certainly don't want to sift through dozens of freshman "How do I find the Consumer Surplus?" questions to find threads dedicated to profile analysis, school field strengths, comparisons of different schools' qualifying exams, news about which professors are transferring between departments, et cetera. That information is actually relevant here, and the scarcity of forums like this lead people to defend its purity somewhat vigorously.

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Originally Posted by moneyandcredit
People are being mean about it because this is one of very few places on the internet where upper-division economics students can get together and discuss graduate school options and strategies [...] threads dedicated to profile analysis, school field strengths, comparisons of different schools' qualifying exams, news about which professors are transferring between departments, et cetera. That information is actually relevant here, and the scarcity of forums like this lead people to defend its purity somewhat vigorously.
A+ for a succinct, to-the-point summary free of malevolence.

To the OP: You shouldn't have to ask this question on an internet board. Any introductory textbook would give you the answer, and, failing that, a Google search will do the trick. It's not that we mind helping; it's just that allowing these kinds of threads to flourish will inevitably clutter the board. That, in turn, will result in exactly the kind of market failure you learn about in econ 101 (the chapter on asymmetric information and health insurance).

9. Good post? |
Originally Posted by moneyandcredit
Yahoo answers is actually a good place to ask these kinds of questions. I post answers to questions like this fairly often over there, but I won't do it here.

People are being mean about it because this is one of very few places on the internet where upper-division economics students can get together and discuss graduate school options and strategies, but there are already other places where one can ask homework questions (both free and paid). If principles students find out that it's also a homework forum, we'll pretty much lose the actual purpose of the forum. The recent question on quintile regression methods was annoying enough, but we certainly don't want to sift through dozens of freshman "How do I find the Consumer Surplus?" questions to find threads dedicated to profile analysis, school field strengths, comparisons of different schools' qualifying exams, news about which professors are transferring between departments, et cetera. That information is actually relevant here, and the scarcity of forums like this lead people to defend its purity somewhat vigorously.
I use Yahoo answers as well, mostly to answer questions (I get a high from being selected the best answer to a question). The problem with Yahoo answer is that those who answers the question almost always provides the full solution to the problem. It doesn't give the student the chance to think more deeply about the problem--thereby allowing them to really understand the concepts. The Physics Forum, on the other hand, have moderators that prohibits the giving of full solutions to questions. They guide your think and allow you to discover the solution yourself. This forum is scarce, but an economics homework forum doesn't even exist (as far as I know)! Consider this a public service announcement for those who have the time and the technical background to set up a forum strictly for homework questions in economics.

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Is it possible to create a "homework help" sub-folder? Such a solution seems to be a good compromise between the purists and those willing to tolerate some students looking for help. Such a solution could also foster positive network externalities for the rest of us.

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