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2 Answers

for rektangel, square hav max area

leng+wide=78, so leng=wide=39

Fisrt let's formulate an equation based on what the word problem is giving us.

The lenght and width of a rectangle have a sum of 78= L + W=78

Then it's asking what dimensions give the maximum area, so you must know your Area equation=

A= L(W)




Now plug this into your area equation

A= (78-W) (W)


Now a very interesting concept can be applied, we need to take the derivative of this equation, and must set A= 0.

0= 78(1)-2W

*The (1) came to be because the derivative of a variable is 1. W^2 was changed to 2w because of the power rule of derrivatives, thsis sttes that  we can  bring out the power in front of the variable and subtract 1 from the exponent so we get 2w^1 which is 2W*

Now move things around and solve for W:



Now plug in value back into the L=78-W equation to solve for L

L= 78- 39


Hope this Helps :)

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