a 1125ft^3 open-top rectangular rank with a square base x ft on a side and y ft deep is to be built with its top flush with the ground to catch runoff water. the costs associated with the tank involve not only the material from which the tank is made but also an excavation charge proportional to the product xy.
a)If the total cost is c=5(x^2+4xy)+10xy, what values of x and y will minimize it?

Question

a 1125ft^3 open-top rectangular rank with a square base x ft on a side and y ft deep is to be built with its top flush with the ground to catch runoff water. the costs associated with the tank involve not only the material from which the tank is made but also an excavation charge proportional to the product xy.
a)If the total cost is c=5(x^2+4xy)+10xy, what values of x and y will minimize it?

anonymous · Answer

you need a table first where you can use the volume, 1125 ft^3
the formula for volume in this setting is (x^2)*y = 1125
so for x = 1 y = 1125
x =2 y = 281.25 and so on

anonymous · Answer

once you have your x and y, you need another table where you have your equation C
and put the x and y values, this should give you the cost and the last part is for you to compare the prices

anonymous · Answer

once you check those number you can still have decimals such as x = 1.5 and solve for y, but dont worry about those until you get to where the cost is about even for the x and y and are easier to solve

anonymous · Answer

i would use excel for this problem makes things way easier

anonymous · Answer

Refer to the attachment.