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Calculus problem please help

  • Thread starter Fiorella
  • Start date
  • #1
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Calculus problem...please help!!!

Homework Statement



Here is a picture of the problem: http://i3.photobucket.com/albums/y62/Phio/23.jpg" [Broken]

Homework Equations



A = xy = 780

cost = 8x+2y

The Attempt at a Solution



c = 8x + (1560/x)

c'= 8 - ( 1560/(x^2) )

0 = 8 - ( 1560/(x^2) )



x^2 = 195

x= [tex]\sqrt{195}[/tex]

x = 13.96 = 14


I don't know what to do from here...I still can't figure out what the answer is. I think it must be either B or D.

Please help...thank you!!!
 
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Answers and Replies

  • #2
rock.freak667
Homework Helper
6,230
31


Find the corresponding value of y.
 
  • #3
17
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oh now I see it...it's obvious. The answer is B.

Thanks!
 

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