anonymous one year ago Math help!

1. anonymous

are you familiar with the topics absolute minima/maxima?

2. anonymous

Yes

3. welshfella

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4. anonymous

What does that mean?

5. welshfella

thats the set up find an expression for the area of the rectangle in term of x and y then convert it to one variable so you can find the derivative and equate this to zero.

6. welshfella

the curve is that of y = 3 - x^2

7. anonymous

So I derive this?

8. welshfella

Area of the rectangle A = 2xy and we know that y = 3 - x^2 so plug this expression for y into the expression for the area to get the area in terms of x then find dA/dx and equate to 0 and solve for x to find maxm required

9. anonymous

* sorry to interfere but quick ques. why is are 2xy? I thought its only xy? thanks!

10. anonymous

a=6x-2x^3?

11. welshfella

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12. welshfella

yes thats correct for the area

13. anonymous

a*x*y is only half the area of the whole thing?

14. welshfella

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15. welshfella

xy is the area of half the box

16. welshfella

agreed?

17. welshfella

- though i got the x and y wrong way round

18. welshfella

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19. welshfella

A = 6x - 2x^3 dA/dx = 6 - 6x^2 = 0 x^2 = 1 x = 1

20. welshfella

oh - talking to myself again!!

21. anonymous

Sorry I lost internet connection yesterday but thank you so much! @welshfella