If x is a prime such that (x4 + 1) is also a prime, then how many values are possible for x.
Explanation:
One of x and x4 + 1, will definitely be even and the other odd.
The only even prime number is 2. Hence, either x = 2 or x4 + 1 = 2
If x4 + 1 = 2 ⇒ x = 1 (not a prime number, hence rejected)
∴ x = 2 and x4 + 1 = 17.
∴ Only one value of x is possible.
Hence, option (b).
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