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Topic: lower-bound quadratic on two other quadratics
Replies: 3   Last Post: Jul 13, 2012 2:27 AM

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Posts: 35
Registered: 8/22/09
Re: lower-bound quadratic on two other quadratics
Posted: Jul 13, 2012 2:27 AM
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On Thu, 12 Jul 2012 12:44:27 +0000 (UTC), AMX <> wrote:
> On Mon, 9 Jul 2012 15:12:44 -0700 (PDT), Armand
><> wrote:

>> Given two positive quadratic functions a1x^2 + b1x + c1 and
>> a2x^2 + b2x + c2, find a third quadratic function which is a
>> "greatest" lower-bound on both these two functions.

> Try:
> 1. Order your functions that a1>=a2
> 2. compute t=(b2-b1)^2/(4*(a2-a1))-c1
> 3. sought y=ax^2+bx+c is such that a=a1, b=b1, c=min(c1,t)

Does not work for a1=a2 and b1!=b2.

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