To solve this problem you must apply the proccedure shown below:
1- You have the following quadratic expression n^2-25.
2. When you factor, you obtain:
(n-5)(n+5)
3. To verify this is true, you can apply the distributive property, as below:
n^2+5n-5n-25
n^2+25
Therefore, as you can see, the answer is the second option, which is:
(n-5)(n+5)