Prove or disprove the following statements:

[nddewaters]

a) Every odd number greater than 3 can be written as the sum of two prime numbers.
b) If n is not a multiple of 3, then n² + 2 is a multiple of 3.
c) If n is an odd number, then n² + 4 is prime.
d) If X ⊆ A and Y ⊆ B , then X ∪ Y ⊆ A ∩ B.

 

[Petek]

You'll probably get better advice if you show what you've already tried.