Hello I am trying to make a function `goldbach :: Integer -> Bool` for interval `[4..n]` that should return `True` only if all elements in that interval is even and can be summed from two prim numbers. So far I have done this.

```
goldbach::Integer->Bool
goldbach n 
    |goldbach2 n == ??? = goldbach (n-2)
    |n==4 = True
    |otherwise = False

goldbach2 :: Integer -> (Integer, Integer)
goldbach2 a = head $
                 filter (\(x,y) -> isPrime x && isPrime y) $
                 map (\e -> (e, a - e)) [3,5..a `div` 2]
where
factors a = filter (isFactor a) [2..a-1]
isFactor a b = a `mod` b == 0
isPrime a = null $ factors a

```

Function `golbach2` result looks like this `goldbac2 28 = (5, 23)`. How should I chek in my 3rd line `goldbach2 n == ??? = goldbach (n-2)` if result of `goldbach2 n` is correct and gives me two prim numbers?