A cylindrical can has a volume of 36πcm^3.The cost of the material used for the top and bottom of the can is four cents per square centimeter. Meanwhile, the cost of material used for the curved side is three cents per square centimeter. Express the cost of constructing the can as a function of its radius r.
參考答案:一个圆柱形罐头体积为 36πcm^3。用来制作罐头顶面和底面的材料成本为每平方厘米 4 美分。同时，制作侧面的材料成本为每平方厘米 3 美分。将制作罐头的成本表达为它的半径 r 的函数
V = πhr^2 = 36π
h = 36/r^2
Sbt = 2πr^2
Ss = 2πrh = 2π*36/r
c = 3Ss + 4Sbt = 216π/r + 8πr^2