Final answer:
To prove the given expression is a square number, we can rewrite it as a perfect square which comes as

Step-by-step explanation:
To prove that the expression
is a square number, we need to show that it can be expressed in the form of k^2 where k is an integer.
Let's simplify the expression step by step:
- Expand the square term:

- Distribute the second term:

- Combine like terms:

Now, we can rewrite the expression as a perfect square:

Therefore, the expression
is a square number because it can be expressed as
