Def even = 2(n) ; n is any integer
Def odd  = 2(m) + 1; m is any integer

Even * Odd = Even

2(n) * (2(m) + 1) = 2(k); k is any integer
4(nm) + 2(n) = 2(k)
2(2nm + n) = 2(k)
2(x) = 2(k)