# jnu sis doubts

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## jnu sis doubts

 can someone please help me with the following questions 1. the utility function u(x) = x^a - 1/ a concave and increasing convex and increasing concave and decreasing convex and decreasing 2 the consumption set c = (x,y) belongs to R ^2 x>= x degree>0 y>=y degree >0 is bounded convex convex and bounded neither convex nor bounded how to measure the elasticity of demand for imports from offer curves? JNU 2013 I need help in q 21, q 24 is the 25th answer c please help thanks
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## Re: jnu sis doubts

 1. The function is increasing because the first derivative is positive for the defined a and is concave because the second derivative is negative for all values a defined. 2. The given set is convex and is bounded below, but it is not bounded above. A set is called bounded if it is both bounded above and below, so in this case it is not bounded, it is only convex.  "I don't ride side-saddle. I'm as straight as a submarine"
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## Re: jnu sis doubts

 @Subhayu: How do you know this Consumption set is convex?
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## Re: jnu sis doubts

 @Viv: U draw the consumption set and and arbitrarily take any two points and make them join by a st line, all points of the st. line joining the two points will always lie within the set, so the set is convex.  "I don't ride side-saddle. I'm as straight as a submarine"
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## Re: jnu sis doubts

 @subhayu...can convex set for consumption be refer to convex preferences?
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## Re: jnu sis doubts

 Could u pls show how did u plot it
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## Re: jnu sis doubts

 In reply to this post by Granpa Simpson Subhayu could you please explain ques 1 ? Is a constant here ? "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."
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## Re: jnu sis doubts

 @Anjali.. 'a' is constant here and it is given in the ques that 0
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## Re: jnu sis doubts

 In reply to this post by Dreyfus @Vaibhav: Preferences are said to be convex if the set "at least as good as" a convex set, or in other words you can say a preference pattern to be convex if the upper contour set is convex, the ones that occur with normal IC's is an example. This is again ensured by the concept of quasiconcavity..!!!!!  "I don't ride side-saddle. I'm as straight as a submarine"
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## Re: jnu sis doubts

 @subhayu...that means in this case especially ...we can say that since preferences are convex ...therefore set is convex... As extremes are not possible here...am I right?
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## Re: jnu sis doubts

 Consumers preference ordering is given by the utility function, since in this case there is nothing specified about the utility function, you cannot infer anything about his/her preferences. Its just that the consumption set is convex, a consumer's preference ordering is said to be convex if you get IC's whose upper contour set in convex. In this case you do not know how this consumer's IC's look like, so you cannot also tell that whether the upper contour set is convex or not. Consumption set and preferences are not the same, consumption sets are general sets however preferences are relations or you may say a mapping, so it needs a specific functional form to get identified.  "I don't ride side-saddle. I'm as straight as a submarine"
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## Re: jnu sis doubts

 @Subhayu..how to plot the diag..i'm not getting it.
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## Re: jnu sis doubts

 "I don't ride side-saddle. I'm as straight as a submarine"
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## Re: jnu sis doubts

 In reply to this post by The Villain Sorry Ron for such a bad and untidy diagram..nywa that will give u a basic idea...!!!  "I don't ride side-saddle. I'm as straight as a submarine"
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## Re: jnu sis doubts

 Its okk man...Thanxx a lot.I got it..Where can i practice such quest fr?
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## Re: jnu sis doubts

 Regarding Sets and functions you can find this type of practice questions in Simon & Blume, however if you just want to get the concept right I think Varian is the best book to go through..!!!  "I don't ride side-saddle. I'm as straight as a submarine"