Show that the surface area of a closed cuboid with square base and given volume is minimum, when it is a cube.

Explanation

To show that the surface area of a closed cuboid with a square base and a given volume is minimized when it is a cube, we can follow these steps:

### Step 1: Define the Variables
Let:
- \( x \) = length of one side of the square base of the cuboid.
- \( y \) = height of the cuboid.
- The volume \( V \) of the cuboid is given by the formula:
\[
...