Saturday, December 5, 2009

How do you work this out?

Jason plans to fence a rectangular area with 180 meters of fencing. He has written the formula A = w(90 - w) to express the area in terms of the width w. What is the maximum possible area enclosed with his fencing?How do you work this out?
A = w(90 - w)





maximum area, take the derivative and solve for w.





A = w(90 - w)


A = 90 w - w^2





(0 = 90 - 2w )%26lt;-derivative


-90 = -2w


w = 45 meters





plug in 45 to calculate the area


A = w(90 - w)


A = 2025 m^2How do you work this out?
Differentiate the function given to get:





dA/dw = 90 - 2w





At max area, dA/dw = 0.





Hence, let 90 - 2w = 0





w = 45





Max A = 45(90 - 45) = 2025 m^2

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