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

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quasi

Posts: 10,451
Registered: 7/15/05
Re: Help Needed in math
Posted: May 1, 2014 10:23 PM
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William Elliot wrote:
>konyberg wrote:
>>William Elliot wrote:
>>>konyberg wrote:
>>>>
>>>>f(x) = (5x + 3) / x^2, x <> 0

>>>
>>>What's f?


Are you blind?

>>I don't understand the question.

>Did you define f as f(x) = (5x - 3)/x^2?

No, he wrote

f(x) = (5x + 3)/x^2

>>>>If a < f(x) for all x, then a has to be less than the
>>>>global minimum of f(x).
>>>>
>>>>The global minimum of f(x) = -25/12.
>>>>
>>>>The largest integer less than this is -3.

>
>f'(x) = 5/x^2 - (5x + 3)/2x^3 = 0;


No.

>The extremum point, x = 3/5 when f(x) = 0,

Presumably you meant when f'(x) = 0, not when f(x) = 0.

>inflection point.

Not when you use the correct f'(x).

>What you're doing is unfathomable.

Unfathomable to you perhaps.

Nevertheless, konyberg's argument is correct.

quasi



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