[SOLVED] Larson 4.1.6 1. The problem statement, all variables and given/known data Prove that there are infinitely many natural numbers a with the following property: The number n^4+a is not prime for any number n. 2. Relevant equations 3. The attempt at a solution I cannot even think of one such natural number a. :( I need to find some way to factor this after we put some restrictions on a. That is we need to express a in a special form that makes this factorable. If a is equal to b^4, it is not necessarily factorable. In fact, I don't know of any power of b that will make it factorable. a cannot be a function of n. I really don't know what to do.