Find the dimensions of the box with volume 1728 cm3 that has minimal surface area. (Let x, y, and z be the dimensions of the box.) (x, y, z)

Respuesta :

Answer:

The dimensions of the box are 12 cm , 12 cm , 12 cm

Step-by-step explanation:

Let x , y and z be the dimensions of box

Volume of box =xyz=1728

[tex]z=\frac{1728}{xy}[/tex]

Surface area of box = [tex]2xy+2yz+2xz=2xy+2y(\frac{1728}{xy})+2x(\frac{1728}{xy})[/tex]

Let [tex]f(x,y)=2xy+2(\frac{1728}{x})+2(\frac{1728}{y})[/tex]

To get minimal surface area

[tex]\frac{\partial f}{\partial x}=0[/tex] and [tex]\frac{\partial f}{\partial y}=0[/tex]

[tex]\frac{\partial(2xy+2(\frac{1728}{x})+2(\frac{1728}{y}))}{\partial x}=0[/tex]

[tex]2y-2(\frac{1728}{x^2})=0[/tex]

[tex]y=\frac{1728}{x^2}[/tex] ----1

[tex]\frac{\partial(2xy+2(\frac{1728}{x})+2(\frac{1728}{y}))}{\partial y}=0[/tex]

[tex]2x-2(\frac{1728}{y^2})=0\\x=\frac{1728}{y^2} \\y^2=\frac{1728}{x}[/tex]

Using 1

[tex](\frac{1728}{x^2} )^2=\frac{1728}{x}[/tex]

x=0 and [tex]x^3=1728[/tex]

Side can never be 0

So,[tex]x^3=1728[/tex]

x=12

[tex]y=\frac{1728}{x^2} \\y=\frac{1728}{12^2}[/tex]

y=12

[tex]z=\frac{1728}{xy}\\z=\frac{1728}{(12)(12)}[/tex]

z=12

The dimensions of the box are 12 cm , 12 cm , 12 cm

Dimensions of side with minimum surface area is 12 cm

Given that;

Volume of box = 1728 cubic centimeter

Find:

Dimensions of side with minimum surface area

Computation:

Dimensions of side with minimum surface area is with cube

So,

Assume; Side = a

Volume of box = side³

Side³ = 1728

Side = ∛1728

Side = 12 cm

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