Hello, NAPA55!

The answers come out rather ugly . . .

A builder must completely fence in 3 adjacent rectangular lots along a roadway.

Each lot must have an area of 675 square metres.

Fencing along the roadway costs $25/metre while side and back fencing costs $10/metre.

Find the dimensions of each lot that minimize the total cost of fencing. Code:

x x x
* = = = = * = = = = * = = = = *
| | | |
| | | |
y| y| |y |y
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* - - - - * - - - - * - - - - *
x x x

There are m of fencing along the road.

At $25/m, its cost is: . dollars.

There are m of back fencing and m of side fencing.

At $10/m, its cost is: . dollars.

The total cost is: . dollars. .[1]

Each lot has an area of 675 mē: .

Substitute into [1]: .

And __that__ is the function we must minimize . . .