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Nov 4 2013 08:26pm
Quote (Azrad @ Nov 4 2013 10:07pm)
two problems with that...
  • never use appoximations unless you are asked too
  • the problem asked for positive solutions for x and y
also without the negative rule above, I can come up with a better solution by inspection: x=-30, y = -1/2
and better than that, x= -60, y = -1/4, and so on.


lol true. i actually just used the instructions for him because he wanted a quick answer and forgot how to properly do this.

Quote (Azrad @ Nov 4 2013 10:25pm)
perhaps you took the integral of the constraint instead of the derivative? Might explain where those e's and natural logs came from...


yup. like a noob who wasn't thinking :P

This post was edited by rx7drifter on Nov 4 2013 08:27pm
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Nov 4 2013 08:33pm
Quote (Speed93 @ Nov 4 2013 09:57pm)
Find positive numbers x and y satifying the equation xy=15 such that the sum 3x+y is as small as possible?

Solve this quick please! whats the values of x and Y!


Answer is:

x = sqrt(5)
y = 3sqrt(5)
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Nov 4 2013 08:33pm
Quote (rx7drifter @ Nov 4 2013 07:26pm)
yup. like a noob who wasn't thinking :P
my classic move is to get waist deep into a problem like that and deiced that 5*7 = 22 or something else crazy.

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