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1. A variable rectangle has a constant perimeter of 20 cm. Find the lengths of the
sides when the area is a maximum.

I take it that the lengths of sides are the same as the x and y values for what would be the maximum point if we were talking about a parabola? However the part I don't understand it the first sentence.

Any help would be appreciated, thanks.
2. (Original post by Kamila_Kamizaki)
A variable rectangle has a constant perimeter of 20 cm. Find the lengths of the
sides when the area is a maximum.

I take it that the lengths of sides are the same as the x and y values for what would be the maximum point if we were talking about a parabola? However the part I don't understand it the first sentence.

Any help would be appreciated, thanks.
You have two equations, and

Solve these simultaneously and form a quadratic equation. Next, either differentiate or complete the square to find the maximum point.
3. (Original post by zeldor711)
You have two equations, and

Solve these simultaneously and form a quadratic equation. Next, either differentiate or complete the square to find the maximum point.
Wouldn't it be 2x+2y=20? If no, why?
4. (Original post by Kamila_Kamizaki)
Wouldn't it be 2x+2y=20? If no, why?
You are correct
5. (Original post by Kamila_Kamizaki)
Wouldn't it be 2x+2y=20? If no, why?
Ahh yes, my mistake. Will edit

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