Question 808199: The number of value of x for which x^4 + 4 is a prime number , where x belongs to Natural number is ?
Answer by CubeyThePenguin(3113)   (Show Source):
You can put this solution on YOUR website! x = 1, x^4 + 4 = 5
x = 2, x^4 + 4 = 20
x = 3, x^4 + 4 = 85
x = 4, x^4 + 4 = 260 ...
The values of x that work are x = -1 and x = 1.
For more analysis and formal proofs, look at this thread: https://www.quora.com/What-is-the-number-of-integral-values-of-x-for-which-x-4+4-is-a-prime-number
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