The problem
Given $x, y \in \mathbb{Z}$, is it possible to determine if $\frac{xy^2}{2}$ is an even number?
$x$ and $y$ are consecutive numbers and $x$ is even.
My attempt
Assuming $n$ is an integer, it can be rewritten as
$$
\frac{2n\times(2n-1)}{2} = n\times(2n-1)\times(2n-1)
$$
Where $(2n-1)$ is always odd, so it all comes down to $n$, which is unknown. However, the tutor said it can be determined for sure. Another way of going about this would be to say $x$ is even and $y$ is odd, so $xy$ is even, therefore $xy^2$ is even as well.
What can be said about $\frac{xy^2}{2}$ though?
Well $\frac{xy^{2}}{2}$ is only even if $xy^{2}$ has a factor of $4 = 2^2$
Therefore, $\frac{xy^2}{2}$ is even always if
$y$ is divisible by two
or
$x$ is divisible by four
However $x$ is even so $y$ cannot be divisible by two since they are consecutive. Therefore $x$ must be divisible by four.