Then difference between the cubes of two numbers is twice the value of the perfect square of a possitive intiger

There are many solutions. But what do you mean with a perfect square of a number. I thought a number IS a perfect square or not.

For example, the difference between 2² and 4² = 12, which is twice the number 6, which is √36

The difference between 2² and 6² = 32, which is twice the number 16, which is a perfect square.

So choose depending on your interpretation of the question... ;-)

Aline graph should be used