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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: 1,703
Registered: 1/8/12
Re: Help Needed in math
Posted: Apr 29, 2014 5:23 AM
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On Mon, 28 Apr 2014, Peter Percival wrote:
> punisher wrote:
>

> > Find the largest values of the integer a for which ax^2-5x-3 is
> > negative for all values of x.


> Minus three.

ax^2 - 5x - 3
(5 +- sqr(25 + 12a)/2a
25 + 12a < 0; a < -25/12

ax^2 - 5x - 3 < -25x^2 / 12 - 5x - 3 < 0 ?
-25x^2 - 60x - 36 = -(5x + 6)^2 <= 0




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