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- Feb 22nd 2008, 09:18 PMdelicate_tearsQuadratic models
- Feb 22nd 2008, 09:28 PMkalagota
if the width is $\displaystyle x$, then the length can be written as $\displaystyle l = 60 - 2x$

and so, $\displaystyle A = x(60 - 2x) = 60x - 2x^2$

for the third question:

solve for first derivative of $\displaystyle A$ and equate it to $\displaystyle 0$ and solve for the value of $\displaystyle x$.. after solving for $\displaystyle x$, substitute it to the $\displaystyle A$ above..