There are three continuous natural numbers. The sum of the square difference of the larger and smaller numbers and the middle natural number must be a multiple of () There is an option in the multiple choice question, a = 0?

There are three continuous natural numbers. The sum of the square difference of the larger and smaller numbers and the middle natural number must be a multiple of () There is an option in the multiple choice question, a = 0?

Hello
Let the number in the middle be a
Then the larger one is a + 1 and the smaller one is A-1
therefore
(a+1)²-(a-1)²+a
=4a+a
=5a
So he must be a multiple of five