x=9^10-3^17 and x/n is an integer. If n is a positive integer that has exactly two factors, how many different values for n are possible?
(A) One
(B) Two
(C) Three
(D) Four
(E) Five
[spoiler]OA=C[/spoiler]
Source: Manhattan GMAT
x=9^10–3^17 and x/n is an integer. If n is a positive
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Since only prime numbers have exactly two factors, we see that n is a prime, and therefore, we can rephrase the question as "how many prime factors does x have?" So we need to prime factorize x:VJesus12 wrote:x=9^10-3^17 and x/n is an integer. If n is a positive integer that has exactly two factors, how many different values for n are possible?
(A) One
(B) Two
(C) Three
(D) Four
(E) Five
[spoiler]OA=C[/spoiler]
Source: Manhattan GMAT
x = 9^10 - 3^17 = (3^2)^10 - 3^17 = 3^20 - 3^17 = 3^17(3^3 - 1) = 3^17(26) = 3^17 * 2 * 13
We see that x has three prime factors.
Answer: C
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