To solve this problem you must apply the proccedure shown below:
1. You have the following quadratic equation given in the problem above:
n²+4n-5; and you have one factor: (n+5)
2. Therefore, you must find a number whose sum with 5 be 4 and when their product be -5. Keeping this on mind, you have:
(n+5)(n-1)
3. To verify it, you can apply the distributive property:
(n+5)(n-1)=n²+4n-5
The answer is: (n-1)