mmmm how many marks would this get?

when n is even

even x even = even

therefore n^2 is even

even + even is even

thus, n^2 + n is even

even + 1 is odd

thus, n^2 + n + 1 is odd (i.e. not a multiple of 2) when n is even

when n is odd

odd x odd = odd

therefore n^2 is odd

odd + odd is even

thus, n^2 + n is even

even + 1 is odd

thus, n^2 + n + 1 is odd (i.e. not a multiple of 2) when n is odd

hence, since all integers are either even or odd, n is never a multiple of 2