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optimization - HSN forum

# optimization

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### #1xlynsey

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Posted 09 September 2006 - 11:16 AM

Ok i am stuck on a question to do with optimization if anyone has the higher maths textbook its ex 6Q q 7a and b. PAGE113 if not:

and it says:

The cross section of a building constructed inside a parabolic framework is shown in the diagram.
a) given that PQ is 2x m show that the shaded area is 6x-2x^3 square metres
b)Find the maximum cross-sectional area of the building.

any help is much appreciated, thanks:)

### #2The Wedge Effect

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Posted 09 September 2006 - 11:21 AM

Which part is the shaded area?

### #3xlynsey

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Posted 09 September 2006 - 11:37 AM

QUOTE(The Wedge Effect @ Sep 9 2006, 12:21 PM)

Which part is the shaded area?

oops, its the rectangle inside the parabla that has a length of 2x

### #4The Wedge Effect

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Posted 09 September 2006 - 01:28 PM

the comes from so that's where it comes from. Now the reasoning for that, I'll need to have a little think about, unless there was another method I didn't spot. Sorry, I really need to brush up on my maths, not having done any maths for nearly seven months now.

Anyway, as for the second part, you simply go through finding the maximum using differentiation through the usual way, as you've probably been shown. The working is virtually identical for any optimisiation problem, for finding minima/maxima.

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