A rectangular plot of farmland will be bounded on one side by a river and on the other three sides by a​ single-strand electric fence. With 2500 m of wire at your​ disposal, what is the largest area you can​ enclose, and what are its​ dimensions?

Respuesta :

Answer:

[tex]A = 781250\,m^{2}[/tex], [tex]x = 625\,m[/tex], [tex]y = 1250\,m[/tex]

Step-by-step explanation:

The perimeter covered by the electric fence in meters is:

[tex]2\cdot x + y = 2500[/tex]

The area of the rectangle is:

[tex]A = x\cdot y[/tex]

[tex]A = x \cdot (2500-2\cdot x)[/tex]

Let differentiate the previous equation and equates to zero:

[tex]2500-4\cdot x = 0[/tex]

The critical point is:

[tex]x = 625\,m[/tex]

By the Second Derivative Text, it is proved that critical point lead to a maximum:

[tex]\frac{d^{2}A}{dx^{2}} = -4[/tex]

The other side of the rectangle is:

[tex]y = 1250\,m[/tex]

The largest area than can be enclosed is:

[tex]A = (625\,m)\cdot (1250\,m)[/tex]

[tex]A = 781250\,m^{2}[/tex]

The dimensions of the triangle are:

[tex]x = 625\,m[/tex]

[tex]y = 1250\,m[/tex]