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Topic: Help Needed in math
Replies: 25   Last Post: May 2, 2014 6:01 PM

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William Elliot

Posts: 1,600
Registered: 1/8/12
Re: Help Needed in math
Posted: Apr 30, 2014 5:50 AM
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On Wed, 30 Apr 2014, konyberg wrote:
> On Wednesday, April 30, 2014 5:02:27 AM UTC+2, William Elliot wrote:
> >
> > > > Find the largest values of the integer a for which ax^2-5x-3 is negative for all values of x.
> > > set a = (5x + 3) / x^2 and find the minima of this function. This will, with
> > > your constraints, give the answer: a = -3

> > 5/x + 3/x^2
> > -5/x^2 - 6/x^3 = 0
> > -5x + -6 = 0
> > x = -6/5
> > a = (-6 + 3)/(36/25) = -25/12
> > Why does the minimum work?

> Are you asking me why it works?
Yes.



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