If the paper is x by y inches, then the printed area is
(x-2)(y-12)
The paper has area
a = xy = x(24/(x-2) + 12) = 12x^2/(x-2)
da/dt = 12x(x-4)/(x-2)^2
da/dt=0 when x=4
So, the printed area is 4x6 and the page is 6x18
Now see what you can do with the other problem
1) A rectangular page is to contain 24 square inches of print. The page has to have a 6-inch margin on top and at the bottom and a 1-inch margin on each side. Find the dimensions of the page that minimize the amount of paper used.
2) A cable runs along a wall from C to P at a cost of $7 per meter, and straight from P to M at a cost of $25 per meter. Let x be the distance from C to P. If M is 48 meters from the nearest point A on the wall where P lies, and A is 106 meters from C, find x such that the cost of installing the cable is minimized and find this cost.
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