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Find the dimensions of a rectangle with perimeter 100 m whose area is as large as possible. (if both values are the same number, enter it into both blanks.)

Respuesta :

dA/dx = 100 - 4x & the 2nd derivative is -4 [i.e. -ve] 
so setting dA/dx to zero will give a maxima 

100 - 4x = 0 
so x = 25 m 

in other words, a rectangle with a given perimeter has the maximum area when it is a square

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