We are given x is a perfect square.
Let us take x in terms of another variable p.
Let us assume square root of x gives a value p (because x is a perfect square, square root of x would give a perfect number).

Squaring both sides, we get

Square cancels a square root, so we get only x on left side.

We need to find the value of x cube.
Taking cube on both sides, we get

Applying power of power rule of exponents (we multiply power of power).

We can see p^6 is also a perfect square.
So, we could say x^3 is also a perfect square.